Migrated BaseForm tests to @testing-library/react

[piotrpospiech]

Is part of #1130

• added new tests to BaseForm RTL suites
• removed enzyme BaseForm tests

I cannot migrate most of BaseForm tests, because it was based on BaseForm context or state. RTL doesn't support testing these cases. I didn't find another aproach to test these cases.

Additional issue is with ignores synchronous errors test. Using RTL, error cannot be catched.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (1a6ca83) 94.66% compared to head (2588b61) 94.60%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1303      +/-   ##
==========================================
- Coverage   94.66%   94.60%   -0.06%     
==========================================
  Files         231      231              
  Lines        3821     3821              
  Branches     1029     1029              
==========================================
- Hits         3617     3615       -2     
  Misses         82       82              
- Partials      122      124       +2     

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[kestarumper]

I don't know about the other it(...)s but we definitely need to think that through.

I'm not sure how much we can count on the CodeCov code coverage.
If for example the autosave functionality is covered somewhere else (e.g. in a theme package) then that's fine, but we can't lose the tested functionalities at all.

[kestarumper]

Nice!
I haven't come up with any other tests so if nobody suggests anything we're good to go.