Automate pandas PR/branch creation based on snippet changes

[zkrolikowski-vl]

Whenever a change is made to test snippets those changes should be integrated into pandas repository.

Automate this as much as possible, even if it was to be semi-automatic.

[zkrolikowski-vl]

pandas-stubs has moved to new repository and will now be managed alongside pandas itself: https://github.com/pandas-dev/pandas-stubs