Ensure file modes passed to PFD are valid.

The documentation already states the supported file modes. Start
enforcing that the modes passed to PFD are one of the ones mentioned
in the documentation.

Bug: 414387646
Test: atest FileUtilsTest
Test: atest CtsContentProviderTestCases
Test: atest CtsContentResolverTestCases
Flag: android.os.enforce_strict_file_mode_check
Change-Id: If8e5d2adf4c09a5ed4a75eae9850b7cd79861199