Prevent R.class static fields and Apache compress library from being removed by proguard.

Resources that are only used in test classes and were not being used in
app's code were getting removed for optimization purposes.

Similarly Apache compress library, which was only being used in tests,
specifially in com.android.documentsui.archives tests, was getting
removed by proguard.

These were causing multiple tests to fail in DocumentsUIGoogleTests
module. Adding keep rules for the static fields and for the apache
compress library fixes the failing test issue.

Bug: 335446899
Bug: 335393830
Test: atest DocumentsUIGoogleTests:<UnitTests>
Change-Id: I947c5f0a8782a966c4e390148db85acdfcaf5191