Add Identity Credential HAL, default implementation, and VTS tests.

IIdentityCredentialStore provides an interface to a secure store for
user identity documents.  This HAL is deliberately fairly general and
abstract.  To the extent possible, specification of the message
formats and semantics of communication with credential verification
devices and issuing authorities (IAs) is out of scope for this HAL.

It provides the interface with secure storage but a
credential-specific Android application will be required to implement
the presentation and verification protocols and processes appropriate
for the specific credential type.

Bug: 111446262
Test: VtsHalIdentityCredentialTargetTest
Test: android.hardware.identity-support-lib-test
Test: CtsIdentityTestCases
Change-Id: I64eb50114d645dd475012ad1b889d2177aaf1d37