Refactor RKP key pool in keystore

Split the IRemotelyProvisionedKeyPool binder implementation to its own
struct, as we cannot have two rust objects backing the same native
binder.

Test: keystore2_test
Test: keystore2_test --ignored
Bug: 194696876
Change-Id: I188bc2e2daf277f4a3543c7ec8320002d57f60ba
2 files changed