Fix chip-tool handling of same-named structs in different clusters.

[bzbarsky-apple]

The chip-tool code was assuming that the only way a struct with the same name could occur in multiple clusters was if it was the same struct, shared by the two clusters. But that's just not true in the spec. For example, there are totally different TargetStruct structs in different clusters.

This fixes chip-tool to do the same thing as cluster-objects in terms of deciding what the set of structs we have to deal with is.

[github-actions]

PR #26253: Size comparison from 85fd5ce to 67639bd

Increases (1 build for cc32xx)

platform	target	config	section	85fd5ce	67639bd	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL	.debug_info	19489249	19489250	1	0.0

Full report (1 build for cc32xx)

platform	target	config	section	85fd5ce	67639bd	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL		0	0	0	0.0
			(read only)	601114	601114	0	0.0
			(read/write)	204132	204132	0	0.0
			.ARM.attributes	44	44	0	0.0
			.ARM.exidx	8	8	0	0.0
			.bss	197544	197544	0	0.0
			.comment	206	206	0	0.0
			.data	1468	1468	0	0.0
			.debug_abbrev	956756	956756	0	0.0
			.debug_aranges	103416	103416	0	0.0
			.debug_frame	349704	349704	0	0.0
			.debug_info	19489249	19489250	1	0.0
			.debug_line	2678035	2678035	0	0.0
			.debug_line_str	513	513	0	0.0
			.debug_loc	33340	33340	0	0.0
			.debug_loclists	1501882	1501882	0	0.0
			.debug_ranges	4984	4984	0	0.0
			.debug_rnglists	96008	96008	0	0.0
			.debug_str	3024877	3024877	0	0.0
			.ramVecs	780	780	0	0.0
			.resetVecs	64	64	0	0.0
			.rodata	104170	104170	0	0.0
			.shstrtab	265	265	0	0.0
			.stack	2048	2048	0	0.0
			.strtab	477531	477531	0	0.0
			.symtab	285936	285936	0	0.0
			.text	494824	494824	0	0.0