Make file lock packet type explicit `FileLockCommunicator` now includes an additional byte that represents the `FileLockPacketType` when sending packets to other processes. `DefaultFileLockContentionHandler` now checks for the `LOCK_RELEASE_CONFIRMATION` type instead of interpreting any packet for a lock for which it already has received a packet as a lock release confirmation.
Adding the additional byte will be ignored by old versions which only read the first 9 bytes. New versions can still read packets from old versions that do not include the byte. They use the `UNKNOWN` type in this case. Thus, this protocol change is backwards compatible.