Fix the "not storing data" mode of ClusterStateCache to actually work.

[bzbarsky-apple]

Since we were storing no data, we were computing clusterSize to 0 for all clusters in GetSortedFilters, and then we were not adding any DataVersion filters into our requests at all.

The fix is that in "don't store data" mode we still store how big the data would have been, so we can correctly prioritize our DataVersion filters.

Without this fix, the change in
#26181 fails CI. That CI also acts as a test for this functionality, once
#26181 happens.

[github-actions]

PR #26187: Size comparison from a14e6fb to 17fd862

Decreases (1 build for cc32xx)

platform	target	config	section	a14e6fb	17fd862	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL	.debug_info	20330829	20330828	-1	-0.0

Full report (1 build for cc32xx)

platform	target	config	section	a14e6fb	17fd862	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL		0	0	0	0.0
			(read only)	643249	643249	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	933224	933224	0	0.0
			.debug_aranges	87792	87792	0	0.0
			.debug_frame	302140	302140	0	0.0
			.debug_info	20330829	20330828	-1	-0.0
			.debug_line	2687904	2687904	0	0.0
			.debug_loc	2838960	2838960	0	0.0
			.debug_ranges	288072	288072	0	0.0
			.debug_str	3042335	3042335	0	0.0
			.ramVecs	780	780	0	0.0
			.resetVecs	64	64	0	0.0
			.rodata	104401	104401	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	377963	377963	0	0.0
			.symtab	256976	256976	0	0.0
			.text	536728	536728	0	0.0