Updates prior to SQLAlchemy 2.0 upgrade

[martinburchell]

Changes for SQLAlchemy 2.0 that are compatible with 1.4 to reduce the number of changes in #385.

I've fixed anything that was broken in the Python tests with deprecation warnings enabled:

SQLALCHEMY_WARN_20=1 pytest -W error::sqlalchemy.exc.RemovedIn20Warning -W error::sqlalchemy.exc.MovedIn20Warning -W error::SADeprecationWarning

I've also fixed any other legacy calls to select() with the columns given in a single list argument. I've added tests where these cases weren't covered.
I've also changed the task test factories to number IDs from 1 instead of 0 and fixed a flaky webview test, which wrongly assumed object IDs would appear in a certain order.

I have not been able to test merge_db.py as I couldn't get it to work.
This error was with two recently created databases:

File "/home/martinb/.virtualenvs/camcops/bin/camcops_server", line 8, in <module>
  sys.exit(main())

File "/home/martinb/workspace/camcops/server/camcops_server/camcops_server.py", line 1593, in main
  retval = camcops_main()

File "/home/martinb/workspace/camcops/server/camcops_server/camcops_server.py", line 1520, in camcops_main
  success = progargs.func(progargs)  # type: Optional[bool]

File "/home/martinb/workspace/camcops/server/camcops_server/camcops_server.py", line 1044, in <lambda>
  func=lambda args: _merge_camcops_db(

File "/home/martinb/workspace/camcops/server/camcops_server/camcops_server.py", line 285, in _merge_camcops_db
  merge_camcops_db(
File "/home/martinb/workspace/camcops/server/camcops_server/cc_modules/merge_db.py", line 1256, in merge_camcops_db
  merge_db(
File "/home/martinb/.virtualenvs/camcops/lib/python3.9/site-packages/cardinal_pythonlib/sqlalchemy/merge_db.py", line 972, in merge_db
  rewrite_relationships(

File "/home/martinb/.virtualenvs/camcops/lib/python3.9/site-packages/cardinal_pythonlib/sqlalchemy/orm_inspect.py", line 445, in rewrite_relationships
  related_new = objmap[related_old]
KeyError: <camcops_server.cc_modules.cc_patient.Patient object at 0x7f91a9b070d0>