Unconditionally generate hash-based proguard mapping files

Previously, this was restricted to targets that enable R8 full mode, but
that was really just a temporary carveout to avoid disrupting other
targets. Since then, R8 full mode has been enabled by default for all
app targets, and the hash-based mapping mechanism is further integrated
into various debugging and retracing pipelines.

As of now, there are are only a very small number of targets that have
enabled optimization/obfuscation and are still using R8 compat mode, so
the build-time impact of this change should be minimal, and there should
be no functional runtime side effects.

Bug: 297566172
Test: m framework-appsearch + inspect proguard mapping
Change-Id: I5dfea60f60dc37b8445c8fddba6a4eab0dc41d96