Most unit tests in this file currently does not assign an lsid and txnNumber to the test oplog entries they use. This is unrealistic since the SessionCatalogMigrationSource only deals with oplog entries for retryable writes and transations. Also, starting from SERVER-63494, the SessionCatalogMigrationSource will need to check the session id of each fetched oplog entry to determine if it corresponds to an internal transaction since internal transaction oplog entries need to be handled differently. To make these unit tests still work in SERVER-63494, the oplog entries they use must each have an lsid (and txnNumber).