Update cache_sdk_system_features aconfig flag bug

Use b/326623529 to more clearly differentiate between separate but related
feature flagged efforts for build-time system feature code stripping and
codegen.

Change-Id: Ifcc880b2ebf1f2d23431ddb4c60ef1bcb5bda175
Test: m
Bug: 326623529
Flag: android.content.pm.cache_sdk_system_features