Further refine system_server Proguard rules

Ensure Activity+View instances are properly kept, and fix JNI interop
for PackageManager shell commands.

Note: Normally Activity/View references are implicitly kept through
manifest and resource entries bundled in the target. system_server is
somewhat unique in that its manifest/resource entries are stored
separately with the framework. Follow-up work will route such references
explicitly to the R8 invocation.

Bug: 221332315,221322925,221346618,221349887
Test: SYSTEM_OPTIMIZE_JAVA=true + atest
  CtsInstalledLoadingProgressHostTests
  CtsAutoFillServiceTestCases
  CtsAppSecurityHostTestCases
  CtsAppTestCases
Change-Id: I347d2264f5ee41931edbd37c62be0a46a834b4c2