Specify flags_packages property in the android_app-generated rro module

Specify the `flags_packages` property in the rro module generated in the
android_app module factory. This property passes the information about
the state of the aconfig flags to aapt2, which enables flagging the
resources in the manifest files.

Test: Patch ag/29933298 && m framework-res
Bug: 374827009
Change-Id: I383c0050efaa160a6038133422eedb70545f1271