Remove most of FDE support

Since Android 10, new devices have been required to use FBE instead of
FDE.  Therefore, the FDE code is no longer needed.

Remove most of cryptfs.cpp.  A few parts of it need to be kept in order
to support the dm-crypt method of adoptable storage encryption.

Keep the FDE-specific binder methods stubbed out for now until their
callers can be removed.

Bug: 191796797
Change-Id: I90b1e4cacd2f3e5cce77a82a0af744fcc7da9400