As part of the authoritative shards program, we need to enable _configsvrCommitChunkMigrationCommand to be invoked from the authoritative path.

The new command is expected to have the following behavior:

• It returns the final version of the migrated chunk.
• It is idempotent: if a previous call already committed the migration, it should still return the final version of the migrated chunk. The command must also succeed even if allowMigrations or allowChunkOperations is disabled after the commit has already completed.
• It accepts retryable writes, since it will be invoked with a session id to provide replay protection.