Untangle SetUpCodePairer from CHIPDeviceCommissioner a bit.

[bzbarsky-apple]

Followup to #16802

Instead of making the behavior of CHIPDeviceCommissioner depend on the
state of the SetUpCodePairer, just have the latter register as the
pairing delegate when it cares about PASE establishment, and restore
the logic we used to have in CHIPDeviceCommissioner before PR 16802.

The one logic change in CHIPDeviceCommissioner other than that is a
fix to ensure that we in fact call OnPairingComplete when PASE is
established even if we're going to proceed to auto-commission, so
SetUpCodePairer knows to get out of the way at that point.

Problem

See discussion at #16802 (comment)

Change overview

See above.

Testing

Ensured that the test steps from #16802 still pass. CI should test the rest, generally.

[github-actions]

PR #16890: Size comparison from fbcaa81 to 20419ad

Increases (1 build for linux)

platform	target	config	section	fbcaa81	20419ad	change	% change
linux	chip-tool-no-interactive-ipv6only	arm64	(read only)	9943796	9944612	816	0.0
			(read/write)	475633	475665	32	0.0
			.data.rel.ro	374024	374056	32	0.0
			.text	8380852	8381620	768	0.0

Decreases (1 build for linux)

platform	target	config	section	fbcaa81	20419ad	change	% change
linux	chip-tool-no-interactive-ipv6only	arm64	.rodata	504332	504284	-48	-0.0

Full report (22 builds for cc13x2_26x2, cyw30739, efr32, esp32, k32w, linux, mbed, nrfconnect, p6, telink)

platform	target	config	section	fbcaa81	20419ad	change	% change
cc13x2_26x2	lock-ftd	LP_CC2652R7	(read only)	667427	667427	0	0.0
			(read/write)	184316	184316	0	0.0
			.bss	81784	81784	0	0.0
			.data	3132	3132	0	0.0
			.rodata	79595	79595	0	0.0
			.text	587352	587352	0	0.0
	lock-mtd	LP_CC2652R7	(read only)	616555	616555	0	0.0
			(read/write)	154500	154500	0	0.0
			.bss	77512	77512	0	0.0
			.data	3132	3132	0	0.0
			.rodata	79475	79475	0	0.0
			.text	536592	536592	0	0.0
	pump-app	LP_CC2652R7	(read only)	686887	686887	0	0.0
			(read/write)	166016	166016	0	0.0
			.bss	82176	82176	0	0.0
			.data	3164	3164	0	0.0
			.rodata	81671	81671	0	0.0
			.text	604732	604732	0	0.0
	pump-controller-app	LP_CC2652R7	(read only)	669159	669159	0	0.0
			(read/write)	183488	183488	0	0.0
			.bss	81920	81920	0	0.0
			.data	3128	3128	0	0.0
			.rodata	78007	78007	0	0.0
			.text	590668	590668	0	0.0
cyw30739	light	cyw930739m2evb_01	(read/write)	609634	609634	0	0.0
			.app_xip_area	516376	516376	0	0.0
			.bss	76004	76004	0	0.0
			.data	600	600	0	0.0
			.rodata	0	0	0	0.0
			.text	0	0	0	0.0
	lock	cyw930739m2evb_01	(read/write)	567146	567146	0	0.0
			.app_xip_area	475424	475424	0	0.0
			.bss	74508	74508	0	0.0
			.data	564	564	0	0.0
			.rodata	0	0	0	0.0
			.text	0	0	0	0.0
	ota-requestor-no-progress-logging	cyw930739m2evb_01	(read/write)	578926	578926	0	0.0
			.app_xip_area	477548	477548	0	0.0
			.bss	83836	83836	0	0.0
			.data	504	504	0	0.0
			.rodata	0	0	0	0.0
			.text	112	112	0	0.0
efr32	lighting-app	BRD4161A	(read only)	930216	930216	0	0.0
			(read/write)	129128	129128	0	0.0
			.bss	127136	127136	0	0.0
			.data	1992	1992	0	0.0
			.text	930208	930208	0	0.0
		BRD4161A+rpc	(read only)	959216	959216	0	0.0
			(read/write)	145088	145088	0	0.0
			.bss	142912	142912	0	0.0
			.data	2172	2172	0	0.0
			.text	959208	959208	0	0.0
	window-app	BRD4161A	(read only)	859832	859832	0	0.0
			(read/write)	127096	127096	0	0.0
			.bss	125224	125224	0	0.0
			.data	1868	1868	0	0.0
			.text	859824	859824	0	0.0
esp32	all-clusters-app	c3devkit	(read only)	970490	970490	0	0.0
			(read/write)	1395138	1395138	0	0.0
			.dram0.bss	62456	62456	0	0.0
			.dram0.data	14220	14220	0	0.0
			.flash.rodata	199544	199544	0	0.0
			.flash.text	970490	970490	0	0.0
			.iram0.text	62016	62016	0	0.0
		m5stack	(read only)	1026223	1026223	0	0.0
			(read/write)	462900	462900	0	0.0
			.dram0.bss	67984	67984	0	0.0
			.dram0.data	34024	34024	0	0.0
			.flash.rodata	229056	229056	0	0.0
			.flash.text	1020839	1020839	0	0.0
			.iram0.text	123107	123107	0	0.0
k32w	light	k32w061+release	(read/write)	707240	707240	0	0.0
			.bss	77992	77992	0	0.0
			.data	1872	1872	0	0.0
			.text	621576	621576	0	0.0
	lock	k32w061+release	(read/write)	706488	706488	0	0.0
			.bss	77960	77960	0	0.0
			.data	1912	1912	0	0.0
			.text	620816	620816	0	0.0
linux	chip-tool-no-interactive-ipv6only	arm64	(read only)	9943796	9944612	816	0.0
			(read/write)	475633	475665	32	0.0
			.bss	40401	40401	0	0.0
			.data	1136	1136	0	0.0
			.data.rel.ro	374024	374056	32	0.0
			.dynamic	560	560	0	0.0
			.got	56264	56264	0	0.0
			.init	24	24	0	0.0
			.init_array	192	192	0	0.0
			.rodata	504332	504284	-48	-0.0
			.text	8380852	8381620	768	0.0
	thermostat-no-ble	arm64	(read only)	2292676	2292676	0	0.0
			(read/write)	148657	148657	0	0.0
			.bss	62849	62849	0	0.0
			.data	1040	1040	0	0.0
			.data.rel.ro	77216	77216	0	0.0
			.dynamic	560	560	0	0.0
			.got	4536	4536	0	0.0
			.init	24	24	0	0.0
			.init_array	360	360	0	0.0
			.rodata	142052	142052	0	0.0
			.text	1926688	1926688	0	0.0
mbed	lock-app	CY8CPROTO_062_4343W+release	(read only)	6224	6224	0	0.0
			(read/write)	2358540	2358540	0	0.0
			.bss	185052	185052	0	0.0
			.data	5760	5760	0	0.0
			.text	1321140	1321140	0	0.0
nrfconnect	all-clusters-app	nrf52840dk_nrf52840	(read/write)	1147827	1147827	0	0.0
			bss	143092	143092	0	0.0
			rodata	143204	143204	0	0.0
			text	786732	786732	0	0.0
p6	all-clusters-app	default	(read/write)	2502872	2502872	0	0.0
			.bss	118488	118488	0	0.0
			.data	2640	2640	0	0.0
			.text	1461136	1461136	0	0.0
	light-app	default	(read/write)	2404360	2404360	0	0.0
			.bss	111944	111944	0	0.0
			.data	2496	2496	0	0.0
			.text	1362624	1362624	0	0.0
	lock-app	default	(read/write)	2367968	2367968	0	0.0
			.bss	111688	111688	0	0.0
			.data	2456	2456	0	0.0
			.text	1326232	1326232	0	0.0
telink	lighting-app	tlsr9518adk80d	(read/write)	791300	791300	0	0.0
			bss	70296	70296	0	0.0
			noinit	40416	40416	0	0.0
			text	561260	561260	0	0.0