[res] Fix the registered shared lib asset caching

We must use the ResourcesManager's ApkAssets cache for the
registered library assets, otherwise each Resources object
is going to create a separate FD and parse the same WebView
apk again, quickly exceeding the system limits for FDs per
process.

+ correctly differentiate the overlays vs apps for the
  registered library paths

Bug: 343567870
Flag: android.content.res.register_resource_paths
Test: atest CtsResourcesTestCases
Change-Id: I089ec2fecc875d758a0a5639e7db77081927a25f