Add an OTA download test to Darwin framework CI.

[bzbarsky-apple]

This tests that we can run all the way through an OTA update that takes multiple BDX blocks to transfer, and that the right data is received on the requestor side.

[github-actions]

PR #25951: Size comparison from bf6dc7b to be245da

Decreases (1 build for cc32xx)

platform	target	config	section	bf6dc7b	be245da	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL	.debug_info	20310332	20310331	-1	-0.0

Full report (1 build for cc32xx)

platform	target	config	section	bf6dc7b	be245da	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL		0	0	0	0.0
			(read only)	645825	645825	0	0.0
			(read/write)	203848	203848	0	0.0
			.ARM.attributes	44	44	0	0.0
			.ARM.exidx	8	8	0	0.0
			.bss	197248	197248	0	0.0
			.comment	194	194	0	0.0
			.data	1480	1480	0	0.0
			.debug_abbrev	933102	933102	0	0.0
			.debug_aranges	87704	87704	0	0.0
			.debug_frame	301596	301596	0	0.0
			.debug_info	20310332	20310331	-1	-0.0
			.debug_line	2681125	2681125	0	0.0
			.debug_loc	2827568	2827568	0	0.0
			.debug_ranges	286448	286448	0	0.0
			.debug_str	3041144	3041144	0	0.0
			.ramVecs	780	780	0	0.0
			.resetVecs	64	64	0	0.0
			.rodata	105953	105953	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	380543	380543	0	0.0
			.symtab	257472	257472	0	0.0
			.text	537752	537752	0	0.0

[github-actions]

PR #25951: Size comparison from a2f3564 to 3fd0102

Full report (1 build for cc32xx)

platform	target	config	section	a2f3564	3fd0102	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL		0	0	0	0.0
			(read only)	644409	644409	0	0.0
			(read/write)	203848	203848	0	0.0
			.ARM.attributes	44	44	0	0.0
			.ARM.exidx	8	8	0	0.0
			.bss	197248	197248	0	0.0
			.comment	194	194	0	0.0
			.data	1480	1480	0	0.0
			.debug_abbrev	933099	933099	0	0.0
			.debug_aranges	87608	87608	0	0.0
			.debug_frame	301328	301328	0	0.0
			.debug_info	20302987	20302987	0	0.0
			.debug_line	2679748	2679748	0	0.0
			.debug_loc	2824679	2824679	0	0.0
			.debug_ranges	286200	286200	0	0.0
			.debug_str	3039406	3039406	0	0.0
			.ramVecs	780	780	0	0.0
			.resetVecs	64	64	0	0.0
			.rodata	105953	105953	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	377422	377422	0	0.0
			.symtab	256768	256768	0	0.0
			.text	536336	536336	0	0.0

[bzbarsky-apple]

Fast-tracking platform-specific test change with platform owner review.