Make overlay config work with immutable non-android overlays

This change renames staticness to mutability and changes the OMS to
query OverlayConfig. Changing the enabled state of immutable overlays
and changing the mutability of overlays causes the overlays to be
reinitialized and the default-enabled states to be reapplied. The
default-enabled state is applied whenever the settings for the overlay
is initialized.

Bug: 135048762
Test: use package manager to dump overlay paths of package with
      static/immutable overlays
Test: verify "cmd overlay dump"
Test: atest OverlayManagerServiceImplTests
Test: atest OverlayManagerServiceImplRebootTests

Change-Id: I791befee7f4c7c6ab5ad69cd5d1f3d85e7424f96