KeyMint: implement getKeyCharacteristics()

getKeyCharacteristics should never return keystore-enforced tags,
so filter those out.

Bug: 186685601
Bug: 188855306
Test: VtsAidlKeyMintTargetTest
Merged-In: I4ef15cbb0a09f9b83d5434707f3a285d6012fea0
Change-Id: I4ef15cbb0a09f9b83d5434707f3a285d6012fea0
Ignore-AOSP-First: already merged in aosp/master
2 files changed