Mypy database + pytest in CI

[qarmin]

• Adds some types to files in database folder
• Adds pytest to CI
• Changed GObject.SIGNAL_RUN_FIRST to GObject.SignalFlags.RUN_FIRST - fixed a lot of deprecated warnings in pytest
• Run CI on pull request and push(previously was only on pull request, but I see that not always PR are created in this project)
• Disabled 2 tests, that fails on my computer, but not on CI - flaky tests are not really usable

Currently pytest fails due strange error(help needed to fix this):

 self = <add_game_dialog.AddGameDialog object at 0x7fbcc07674c0 (uninitialized at 0x(nil))>
args = ()
kwargs = {'border_width': 0, 'title': 'Add a new game', 'transient_for': None, 'use_header_bar': True}

    def __init__(self, *args, **kwargs):
        if not initialized:
>           raise RuntimeError(
                "Gtk couldn't be initialized. "
                "Use Gtk.init_check() if you want to handle this case.")
E           RuntimeError: Gtk couldn't be initialized. Use Gtk.init_check() if you want to handle this case.

/opt/hostedtoolcache/Python/3.8.18/x64/lib/python3.8/site-packages/gi/overrides/Gtk.py:508: RuntimeError

Database typing is quite tricky, because python type every variable from database as Any.

Rest of typing should do person that knows better code/structure of app/real variable types