Identity Credential: Restrict AccessControlProfile identifiers to 32.

In order to implement Identity Credential on resource-restricted
secure hardware, we need to limit the number of possible
AccessControlProfile in a credential. A limit of 32 means that such
hardware only need to devote four bytes of RAM for a bitmask with
information about which profiles are authorized.

Document this, add new VTS test, and update the default
implementation.

Bug: 155100967
Test: atest android.security.identity.cts
Test: atest VtsHalIdentityTargetTest
Merged-In: Ia4f2ee0013b330561df744e0595f298a0d156122
Change-Id: I2dd672447bedfa9407bf1044e6261af26fd137f9