This PR add support for TLog encryption through commit proxy. The encryption is done on per-mutation basis. As CP writes mutations to TLog, it inserts encryption header alongside encrypted mutations. Storage server (and other consumers of TLog such as storage cache and backup worker) decrypts the mutations as they peek TLog.
Adding encryption support for TxnStateStore. It is done by supporting encryption. for KeyValueStoreMemory. The encryption is currently done on operation level when the operations are being write to the underlying log file. See inline comment for the encrypted data format.
This PR depends on #7252. It is part of the effort to support TLog encryption #6942.
Adding GetEncryptCipherKeys and GetLatestCipherKeys helper actors, which encapsulate cipher key fetch logic: getting cipher keys from local BlobCipherKeyCache, and on cache miss fetch from EKP (encrypt key proxy). These helper actors also handles the case if EKP get shutdown in the middle, they listen on ServerDBInfo to wait for new EKP start and send new request there instead.
The PR also have other misc changes:
* EKP is by default started in simulation regardless of. ENABLE_ENCRYPTION knob, so that in restart tests, if ENABLE_ENCRYPTION is switch from on to off after restart, encrypted data will still be able to be read.
* API tweaks for BlobCipher
* Adding a ENABLE_TLOG_ENCRYPTION knob which will be used in later PRs. The knob should normally be consistent with ENABLE_ENCRYPTION knob, but could be used to disable TLog encryption alone.
This PR is split out from #6942.
Yi Wu