Migrate to SQLAlchemy 1.4

[mgrabovsky]

There are some big changes coming in SQLAlchemy 1.4 (the biggest one for us being the deprecation of autocommit) and we should be prepared once it hits the repositories.

Although 1.4 has only been released in March 2021 and 1.3 is still going strong as of mid-2021, we should begin to prepare for a migration to 1.4 (or even 2.0) in the future.

Some probing in this direction has been done in #973.

[mgrabovsky]

Fedora 35 now has SQLAlchemy 1.4 and builds seem to be failing because of that. Better take a look at this again.