Continue populating legacy data structures.

Previous work implemented getRequestedPermissions() by dynamically
constructing the legacy list of requested permissions, along with a
deprecation message to migrate to ParsedUsesPermission, but there
are too many callers to migrate at this stage of the release.

For now, to mitigate performance issues that arose, this change
builds a parallel list of requested permissions to avoid the
overhead of dynamically building the legacy list.

Bug: 183223056
Test: atest FrameworksServicesTests:PackageParserTest
Test: atest com.android.server.pm.parsing
Test: atest -p core/java/android/content/pm \
            core/java/com/android/internal/content \
            services/core/java/com/android/server/pm \
            services/tests/servicestests/src/com/android/server/pm
Change-Id: I538fbc12a9fd34f5ad5d63177ac5a2cb9a1ff3ce