Simplify the logic in invokeCommandWithEndpointID in MTRBaseDevice.

[bzbarsky-apple]

• Fix MTRInvokeCallback to guarantee callback delivery, similar to Handle an (invalid) empty InvokeResponses list. #25197
• Fix NSObjectCommandCallback to guarantee callback delivery and ensure that it only calls a single callback.
• Simplify the logic in invokeCommandWithEndpointID by relying on the now-enforced invariants around callbacks.
• Document how errors are delivered for invokeCommandWithEndpointID.

[github-actions]

PR #25199: Size comparison from e0e3225 to fc3824f

Increases (1 build for cc32xx)

platform	target	config	section	e0e3225	fc3824f	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL	.debug_info	20256439	20256440	1	0.0

Full report (1 build for cc32xx)

platform	target	config	section	e0e3225	fc3824f	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL		0	0	0	0.0
			(read only)	642529	642529	0	0.0
			(read/write)	203672	203672	0	0.0
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			.ARM.exidx	8	8	0	0.0
			.bss	197072	197072	0	0.0
			.comment	194	194	0	0.0
			.data	1480	1480	0	0.0
			.debug_abbrev	930533	930533	0	0.0
			.debug_aranges	87392	87392	0	0.0
			.debug_frame	300100	300100	0	0.0
			.debug_info	20256439	20256440	1	0.0
			.debug_line	2656005	2656005	0	0.0
			.debug_loc	2796891	2796891	0	0.0
			.debug_ranges	281688	281688	0	0.0
			.debug_str	3018892	3018892	0	0.0
			.ramVecs	780	780	0	0.0
			.resetVecs	64	64	0	0.0
			.rodata	105817	105817	0	0.0
			.shstrtab	232	232	0	0.0
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			.strtab	377598	377598	0	0.0
			.symtab	256144	256144	0	0.0
			.text	534588	534588	0	0.0