ff32840387
This patch moves the `session_id` field from EncryptionInfo to AlgorithmInfo::MegolmV1AesSha2 as it is specific to Megolm. We provide transparent migration of the serialized data from one format to the other. In the future we plan to reuse `EncryptionInfo` for to_device decryption (using olm not megolm). So megolm session_id should move to algorithm specific data.