Run matrix of compatibility checks for providers

[potiuk]

Provider's compatibility checks have been run for one Python version
and one Airflow version. However provider compatibility is a bit more
nuanced:

• some providers are 2.5.0+, some are 2.6.0+, some are 2.7.0+
• some proivders do not work on Python 3.8 (cohere for importlib
  incompatibility reasons) and we need to run the checks on Python 3.9

This PR adds the following capabilities:

• adds option to install airflow from github URL (finally not used
  in this PR but good to leave it in)
• the non-default Python checks are only run in case we already build CI
  imagese for those Python versions are already built
• builds Airflow vith dev0 version to account for pip comparision
  not allowing for selective -pre flags

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[potiuk]

cc: @eladkal - I thinkk that one has a chance to go green and once merged, you should be able to bump min version easily (I also included more detailed description on how bumping should look like as it will require to remove the old compatibility check from 2.5.0). It turns out that 2.7.0 had a bug fixed in 2.7.1 (apparently) about thread._Rlock pickling during importing (so I have to base all checks for 2.7 on 2.7.1) -but that's fine.