* Deprecate database attribute allow_run_sync
There's really 2 modes of operations in SQL Lab, sync or async
though currently there are 2 boolean flags: allow_run_sync and
allow_run_async, leading to 4 potential combinations, only 2 of which
actually makes sense.
The original vision is that we'd expose the choice to users and they
would decide which `Run` or `Run Async` button to hit.
Later on we decided to have a
single button and for each database to be either sync or async.
This PR cleans up allow_run_sync by removing references to it.
* Fix build
* Add db migration
* using batch_op
