Reduce over-severe logging

Reduce the number of error logs that are emitted by Keystore on a normal
start-up:

- StrongBox is optional, so if its hardware type is unavailable, don't
  treat that as an error.
- Helper text for `deleteAllKeys`.
- Swap "unexpected" for domain info.
- Also remove unnecessary `pub` instances.

Test: boot Cuttlefish, watch logcat
Change-Id: I7c2a7a3ad05a5afedf2b3f3cdba1136a38183183