Add <staging-public-group> tags to SV2

To prevent apps from having to respin atomically with SDK finalization,
<staging-public-group> must be created with type ids that do not
overlap the public resource id namespace.

For SV2, start allocating type ids at 0xff and decrement to get
additional type ids.

Bug: 188463919
Test: builds
Change-Id: Ia7835d04d988127d061d3a454b8391294346a915
Merged-In: Ia7835d04d988127d061d3a454b8391294346a915