Assigned package ids to overlays last

Before overlays could reference internal resources, overlays were
added to AssetManagers before shared libraries. Overlays are now
loaded as shared libraries so they must be assigned package ids
after non-overlay shared libraries so enabling and disabling
overlays does not affect the package ids of the non-overlay shared
libraries.

Since overlays are added to the end of the AssetManager by
ResourcesManager, enabling and disabling overlays will not change
the assets cookie of shared libraries loaded through ResourcesManager,
but it will change the apk assets cookie or overlays added through
AssetManager#addAssetPathAsSharedLibrary.

The package ids of shared libraries added through
AssetManager#addAssetPathAsSharedLibrary will not be affected by
overlays since overlay package ids are assigned last.

Bug: 146685730
Test: CtsHostsideWebViewTests
Change-Id: If7ea17d51b18769bf2465e29af3ae6a71004d06c