Allow overriding android_library_import manifests

Some of the androidx libraries have a transformed manifest
alongside that needs to be used to avoid introducing extra
androidx.startup provider entries.  Add a manifest property
that allows overriding the manifest provided by the aar file.

Bug: 336549758
Test: examine PermissionController.apk
Ignore-AOSP-First: submitting in topic with internal CL
Merged-In: I5c8daf810d2fde9a150cbfe48b4f4216f5d1ba0d
Change-Id: I5c8daf810d2fde9a150cbfe48b4f4216f5d1ba0d