Partially delete unused EITF code

Delete the unused code that was written in 2019 as part of the
Encryption in the Framework project. This change is preparatory to
making the backup transport AIDL async and avoids having to implement
async communication for dead code.

Bug: 202716271
Test: m -j
Change-Id: I57cbb9e6a7d3350e1a278c60fced6618018b3488