Change default caps for BOUND_TOP to superset FGS

This prevents test issues where the proc state upgrades to BOUND_TOP,
and the test loses capabilities (possible during GTS).

The code in a few locations seems to assume that the default caps
strictly increase as PROC_STATE becomes more important, which is also
easier to reason about.

Fixes: 351860676
Test: Compiles, strict increase in caps, under instrumentation only
Flag: EXEMPT, only affects tests
Change-Id: I7c959931044604f7d3254ebeddcf6c9deb2ca75c