Remove CryptKeeperSettings

FDE support has been removed in favor of FBE, so remove the FDE settings
from the "Encryption & credentials" page of the Settings app.

For now I didn't change the way the page appears on devices that don't
use FDE; as before, it still lists "Encrypt phone", followed by either
"Encrypted" or "Phone not encrypted" with no changeable settings.  Note
that the strings used for this have "crypt_keeper" in their names but
aren't specific to FDE; the next CL will rename them.

Test: On Cuttlefish with and without encryption enabled, tested visiting
      the "Encryption & credentials" settings.
Bug: 208476087
Change-Id: I3ce9894291ea1f1886f21980a86a92bfce38038a
(cherry picked from commit 36609c18)
Merged-In: I3ce9894291ea1f1886f21980a86a92bfce38038a