keystore2: rename the ScreenLockBound superencryption keys and type

Rename the ScreenLockBound superencryption keys and superencryption type
to UnlockedDeviceRequired.  This avoids confusion about what "screen
lock bound" means and makes the terminology consistent with the
UnlockedDeviceRequired key parameter in the API.

Bug: 296464083
Test: atest -p --include-subdirs system/security/keystore2
Test: atest CtsKeystoreTestCases
Flag: exempt, mechanical refactoring and comment changes
Change-Id: I98f7716d05c06f8c6db0f3eb616fb6e780407c2d
4 files changed