Bump to GNOME 47 runtime, migrate CI to flatter

[AsciiWolf]

Closes #348.

[tchx84]

@AsciiWolf would you be interested in trying to port this project's CI to flatter? like I use with Gameeky and Flatseal ?

EDIT: This way, we won't need to to test anything else elsewhere.

[AsciiWolf]

@tchx84 Done. :-)

[tchx84]

@tchx84 Done. :-)

good start! it's just missing pytest, black and pyflakes dependencies so the actual tests can run, see Gameeky as an example:

• https://github.com/tchx84/Gameeky/blob/main/dev.tchx84.Gameeky.json#L38
• https://github.com/tchx84/Gameeky/blob/main/tests/requirements.json

[AsciiWolf]

  [0/1] Running all tests.
  1/5 Validate desktop file OK              0.01s
  2/5 Validate schema file  OK              0.01s
  3/5 pyflakes              OK              0.55s
  4/5 black                 OK              1.20s
  5/5 pytest                OK              1.43s
  
  Ok:                 5   
  Expected Fail:      0   
  Fail:               0   
  Unexpected Pass:    0   
  Skipped:            0   
  Timeout:            0   

[tchx84]

  [0/1] Running all tests.
  1/5 Validate desktop file OK              0.01s
  2/5 Validate schema file  OK              0.01s
  3/5 pyflakes              OK              0.55s
  4/5 black                 OK              1.20s
  5/5 pytest                OK              1.43s
  
  Ok:                 5   
  Expected Fail:      0   
  Fail:               0   
  Unexpected Pass:    0   
  Skipped:            0   
  Timeout:            0   

Awesome, only the appstream validation is missing now :)

EDIT: see https://github.com/tchx84/Gameeky/blob/main/data/meson.build#L62

[AsciiWolf]

  [0/1] Running all tests.
  1/6 Validate desktop file   OK              0.01s
  2/6 Validate schema file    OK              0.01s
  3/6 Validate appstream file OK              0.02s
  4/6 pyflakes                OK              0.51s
  5/6 black                   OK              1.15s
  6/6 pytest                  OK              1.37s
  Ok:                 6   
  Expected Fail:      0   
  Fail:               0   
  Unexpected Pass:    0   
  Skipped:            0   
  Timeout:            0   

Done. :-)