Change the flat request matching logic

Currently the flattened request matching logic
does not support subset checks. We need that to
fully support mdoc element matching.

Bug: 272334103
Test: atest FrameworksServicesTests:com.android.server.credentials.CredentialDescriptionRegistryTest
Change-Id: I7904570146426d33dbf8325c01a825787d1648f0
2 files changed