Add APIs to support granting access to Android Keystore keys

To this point, there has been no way for an app to grant access
to keys it owns in the Android Keystore to other apps on the
device. This commit adds a new KeyStoreManager class that
interfaces with the KeyStoreService to support granting and
revoking access to keys as well as for a grantee app to access
a key in the grant domain through the key's ID.

Bug: 351158708
Test: atest KeyStoreManagerTest
Change-Id: Id2d785228fa852b21324d2792e3f34c27756034d