Remove unused definitions from types_stub.h.

[bzbarsky-apple]

Some of these were used but only by dead code, so some dead code is removed too.

[github-actions]

PR #25138: Size comparison from 50ed10e to 7ff4c37

Decreases (1 build for cc32xx)

platform	target	config	section	50ed10e	7ff4c37	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL	.debug_abbrev	930151	930005	-146	-0.0
			.debug_aranges	87464	87416	-48	-0.1
			.debug_frame	300232	300116	-116	-0.0
			.debug_info	20330253	20327108	-3145	-0.0
			.debug_line	2658243	2657881	-362	-0.0
			.debug_loc	2791404	2790854	-550	-0.0
			.debug_ranges	281600	281552	-48	-0.0
			.debug_str	3015052	3010599	-4453	-0.1

Full report (1 build for cc32xx)

platform	target	config	section	50ed10e	7ff4c37	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL		0	0	0	0.0
			(read only)	641857	641857	0	0.0
			(read/write)	204124	204124	0	0.0
			.ARM.attributes	44	44	0	0.0
			.ARM.exidx	8	8	0	0.0
			.bss	197528	197528	0	0.0
			.comment	194	194	0	0.0
			.data	1476	1476	0	0.0
			.debug_abbrev	930151	930005	-146	-0.0
			.debug_aranges	87464	87416	-48	-0.1
			.debug_frame	300232	300116	-116	-0.0
			.debug_info	20330253	20327108	-3145	-0.0
			.debug_line	2658243	2657881	-362	-0.0
			.debug_loc	2791404	2790854	-550	-0.0
			.debug_ranges	281600	281552	-48	-0.0
			.debug_str	3015052	3010599	-4453	-0.1
			.ramVecs	780	780	0	0.0
			.resetVecs	64	64	0	0.0
			.rodata	105697	105697	0	0.0
			.shstrtab	232	232	0	0.0
			.stab	204	204	0	0.0
			.stabstr	441	441	0	0.0
			.stack	2048	2048	0	0.0
			.strtab	376514	376514	0	0.0
			.symtab	256016	256016	0	0.0
			.text	534036	534036	0	0.0