Use fs-verity for protecting updatable font files.

- Updatable font files should have fs-verity enabled.
- PostScript name metadata is checked to detect if files are swapped.
- Font revision metadata is checked to detect if version downgrade
  happens.

Bug: 176939176
Test: atest FrameworksServicesTests:UpdatableFontDirTest
Change-Id: Ie59012e17ef4f9db2419db259e0773067ace4120