[tabs] fix pb with non-lazy tabs: style isn't properly set due to missing jquery.ui activation. Closes #2465657 also do a small cleanup on the way, and properly implements render_entity rather than cell_call, as one would expect regarding default PrimaryView code.

[migration] fix backward compat for rename_relation

[datafeed] make cnxset handling of datafeed source more robust currently we may run in some cases where the session has no more cnxset depending on errors and parser's handling of the cnxset. Also, free the cnxset and reacquire it later, letting a chance to other threads to run.