Rename crypt_keeper_* strings that are still used

Some strings used in the Settings UI have "crypt_keeper" in their names,
but they aren't specific to FDE, which is no longer supported.  They are
still used to report the encrypted status of the device on devices that
use FBE, or the unencrypted status of the device on devices that don't
have encryption enabled at all.  Rename these strings appropriately.

Test: On Cuttlefish with and without encryption enabled, tested visiting
      the "Encryption & credentials" settings.
Bug: 208476087
Change-Id: Ic63910c870837f5b37e4407ba5b3c7629e925c17
(cherry picked from commit 6552bdd0)
Merged-In: Ic63910c870837f5b37e4407ba5b3c7629e925c17