[incfs] Implement an API to check for the full mount loaded status

IncFs_IsEverythingFullyLoaded() returns the status of the whole
mount, and does it in the most optimal way available in the
driver - v2 uses the .incomplete/ directory, while the older
version lists all files and checks their statuses one by one

Bug: 183067554
Test: atest libincfs-test
Change-Id: Ia958e18f44397ace791f33b68a6b89d5e0268f83
6 files changed
tree: 4b7618b104f15680f198aec4fa1ed9124a43b04d
  1. incfs/
  2. libdataloader/
  3. sysprop/
  4. .clang-format
  5. METADATA
  6. PREUPLOAD.cfg