Fix detection of negative integers when floating point is expected.

[bzbarsky-apple]

Our "see if it's an integer and append .0" code for floating point
only detected positive integers, so we were ending up with things like
"-1f" in generated code, which does not compile.

Fixes #19800

Problem

See above.

Change overview

Fixes the regexp and enable some tests that now compile.

Testing

The new code compiles, and we'll see how it does in CI.

[github-actions]

PR #19821: Size comparison from 89c5d50 to 924bc23

Increases (5 builds for cc13x2_26x2, linux, nrfconnect, telink)

platform	target	config	section	89c5d50	924bc23	change	% change
cc13x2_26x2	all-clusters-app	LP_CC2652R7	(read only)	660127	660135	8	0.0
			.text	572576	572584	8	0.0
linux	chip-tool-no-interactive-ipv6only	arm64	(read only)	9887356	9887980	624	0.0
			.rodata	473180	473196	16	0.0
			.text	7877748	7878356	608	0.0
nrfconnect	all-clusters-app	nrf52840dk_nrf52840	(read/write)	1199911	1199927	16	0.0
			text	823092	823096	4	0.0
telink	light-switch-app	tlsr9518adk80d	text	560390	560392	2	0.0
	lighting-app	tlsr9518adk80d	text	576850	576852	2	0.0

Decreases (2 builds for cc13x2_26x2, efr32)

platform	target	config	section	89c5d50	924bc23	change	% change
cc13x2_26x2	all-clusters-app	LP_CC2652R7	(read/write)	190744	190736	-8	-0.0
efr32	lock-app	BRD4161A+wf200	(read only)	967144	967128	-16	-0.0
			.text	967136	967120	-16	-0.0

Full report (30 builds for cc13x2_26x2, cyw30739, efr32, esp32, k32w, linux, mbed, nrfconnect, p6, telink)

platform	target	config	section	89c5d50	924bc23	change	% change
cc13x2_26x2	all-clusters-app	LP_CC2652R7	(read only)	660127	660135	8	0.0
			(read/write)	190744	190736	-8	-0.0
			.bss	73764	73764	0	0.0
			.data	3356	3356	0	0.0
			.rodata	87239	87239	0	0.0
			.text	572576	572584	8	0.0
	all-clusters-minimal-app	LP_CC2652R7	(read only)	648947	648947	0	0.0
			(read/write)	157324	157324	0	0.0
			.bss	73052	73052	0	0.0
			.data	3356	3356	0	0.0
			.rodata	90771	90771	0	0.0
			.text	557856	557856	0	0.0
	lock-ftd	LP_CC2652R7	(read only)	691535	691535	0	0.0
			(read/write)	149448	149448	0	0.0
			.bss	70764	70764	0	0.0
			.data	3280	3280	0	0.0
			.rodata	99551	99551	0	0.0
			.text	591500	591500	0	0.0
	lock-mtd	LP_CC2652R7	(read only)	640951	640951	0	0.0
			(read/write)	143896	143896	0	0.0
			.bss	66500	66500	0	0.0
			.data	3280	3280	0	0.0
			.rodata	99431	99431	0	0.0
			.text	541028	541028	0	0.0
	pump-app	LP_CC2652R7	(read only)	672799	672799	0	0.0
			(read/write)	169072	169072	0	0.0
			.bss	70884	70884	0	0.0
			.data	3280	3280	0	0.0
			.rodata	87903	87903	0	0.0
			.text	584412	584412	0	0.0
	pump-controller-app	LP_CC2652R7	(read only)	658675	658675	0	0.0
			(read/write)	183308	183308	0	0.0
			.bss	70996	70996	0	0.0
			.data	3276	3276	0	0.0
			.rodata	83747	83747	0	0.0
			.text	574448	574448	0	0.0
	shell	LP_CC2652R7	(read only)	689870	689870	0	0.0
			(read/write)	156496	156496	0	0.0
			.bss	76060	76060	0	0.0
			.data	3360	3360	0	0.0
			.rodata	110022	110022	0	0.0
			.text	579536	579536	0	0.0
cyw30739	light	cyw930739m2evb_01	(read/write)	613246	613246	0	0.0
			.app_xip_area	469896	469896	0	0.0
			.bss	86304	86304	0	0.0
			.data	728	728	0	0.0
			.rodata	0	0	0	0.0
			.text	112	112	0	0.0
	lock	cyw930739m2evb_01	(read/write)	610626	610626	0	0.0
			.app_xip_area	467100	467100	0	0.0
			.bss	86480	86480	0	0.0
			.data	732	732	0	0.0
			.rodata	0	0	0	0.0
			.text	112	112	0	0.0
	ota-requestor-no-progress-logging	cyw930739m2evb_01	(read/write)	617134	617134	0	0.0
			.app_xip_area	474672	474672	0	0.0
			.bss	85472	85472	0	0.0
			.data	672	672	0	0.0
			.rodata	0	0	0	0.0
			.text	112	112	0	0.0
efr32	lighting-app	BRD4161A	(read only)	925456	925456	0	0.0
			(read/write)	132424	132424	0	0.0
			.bss	130344	130344	0	0.0
			.data	2080	2080	0	0.0
			.text	925448	925448	0	0.0
		BRD4161A+rpc	(read only)	961160	961160	0	0.0
			(read/write)	149304	149304	0	0.0
			.bss	147016	147016	0	0.0
			.data	2284	2284	0	0.0
			.text	961152	961152	0	0.0
		BRD4161A+rs911x	(read only)	800804	800804	0	0.0
			(read/write)	128700	128700	0	0.0
			.bss	126612	126612	0	0.0
			.data	2088	2088	0	0.0
			.text	800796	800796	0	0.0
	lock-app	BRD4161A+wf200	(read only)	967144	967128	-16	-0.0
			(read/write)	129076	129076	0	0.0
			.bss	126988	126988	0	0.0
			.data	2088	2088	0	0.0
			.text	967136	967120	-16	-0.0
	window-app	BRD4161A	(read only)	910600	910600	0	0.0
			(read/write)	132528	132528	0	0.0
			.bss	130416	130416	0	0.0
			.data	2108	2108	0	0.0
			.text	910592	910592	0	0.0
esp32	all-clusters-app	c3devkit	(read only)	1013700	1013700	0	0.0
			(read/write)	1483554	1483554	0	0.0
			.dram0.bss	69400	69400	0	0.0
			.dram0.data	14632	14632	0	0.0
			.flash.rodata	214080	214080	0	0.0
			.flash.text	1013700	1013700	0	0.0
			.iram0.text	62902	62902	0	0.0
		m5stack	(read only)	1068163	1068163	0	0.0
			(read/write)	485640	485640	0	0.0
			.dram0.bss	74920	74920	0	0.0
			.dram0.data	34144	34144	0	0.0
			.flash.rodata	244580	244580	0	0.0
			.flash.text	1062779	1062779	0	0.0
			.iram0.text	123267	123267	0	0.0
k32w	light	k32w061+release	(read/write)	659604	659604	0	0.0
			.bss	68764	68764	0	0.0
			.data	1992	1992	0	0.0
			.text	583048	583048	0	0.0
	lock	k32w061+release	(read/write)	722156	722156	0	0.0
			.bss	69204	69204	0	0.0
			.data	2000	2000	0	0.0
			.text	645152	645152	0	0.0
linux	chip-tool-no-interactive-ipv6only	arm64	(read only)	9887356	9887980	624	0.0
			(read/write)	674225	674225	0	0.0
			.bss	42641	42641	0	0.0
			.data	1152	1152	0	0.0
			.data.rel.ro	613208	613208	0	0.0
			.dynamic	528	528	0	0.0
			.got	13416	13416	0	0.0
			.init	24	24	0	0.0
			.init_array	192	192	0	0.0
			.rodata	473180	473196	16	0.0
			.text	7877748	7878356	608	0.0
	thermostat-no-ble	arm64	(read only)	2575988	2575988	0	0.0
			(read/write)	180577	180577	0	0.0
			.bss	87889	87889	0	0.0
			.data	1688	1688	0	0.0
			.data.rel.ro	82928	82928	0	0.0
			.dynamic	528	528	0	0.0
			.got	5056	5056	0	0.0
			.init	24	24	0	0.0
			.init_array	400	400	0	0.0
			.rodata	164196	164196	0	0.0
			.text	2172720	2172720	0	0.0
mbed	lock-app	CY8CPROTO_062_4343W+release	(read only)	6224	6224	0	0.0
			(read/write)	2439072	2439072	0	0.0
			.bss	208212	208212	0	0.0
			.data	5864	5864	0	0.0
			.text	1401716	1401716	0	0.0
nrfconnect	all-clusters-app	nrf52840dk_nrf52840	(read/write)	1199911	1199927	16	0.0
			bss	141606	141606	0	0.0
			rodata	156312	156312	0	0.0
			text	823092	823096	4	0.0
	all-clusters-minimal-app	nrf52840dk_nrf52840	(read/write)	1147887	1147887	0	0.0
			bss	140858	140858	0	0.0
			rodata	132840	132840	0	0.0
			text	795316	795316	0	0.0
p6	all-clusters-app	default	(read/write)	2555392	2555392	0	0.0
			.bss	143392	143392	0	0.0
			.data	2776	2776	0	0.0
			.text	1513656	1513656	0	0.0
	all-clusters-minimal-app	default	(read/write)	2501240	2501240	0	0.0
			.bss	142672	142672	0	0.0
			.data	2776	2776	0	0.0
			.text	1459504	1459504	0	0.0
	light-app	default	(read/write)	2432000	2432000	0	0.0
			.bss	134752	134752	0	0.0
			.data	2592	2592	0	0.0
			.text	1390264	1390264	0	0.0
	lock-app	default	(read/write)	2452712	2452712	0	0.0
			.bss	134576	134576	0	0.0
			.data	2600	2600	0	0.0
			.text	1410976	1410976	0	0.0
telink	light-switch-app	tlsr9518adk80d	(read/write)	790472	790472	0	0.0
			bss	69900	69900	0	0.0
			noinit	40416	40416	0	0.0
			text	560390	560392	2	0.0
	lighting-app	tlsr9518adk80d	(read/write)	810184	810184	0	0.0
			bss	70148	70148	0	0.0
			noinit	40416	40416	0	0.0
			text	576850	576852	2	0.0