Gtk4 support

[orontee]

Context

See 📢 Collecting ideas for future milestones for motivations.

Analysis

• Adapt current version as explained in Preparation in GTK 3.x

  Simplify UI files:

  find argos/ui -type f -name "*.ui" -execdir gtk-builder-tool simplify --replace {} \;
  

• Apply changes that need to be done at the migration time

  To convert UI files:

  find argos/ui -type f -name "*.ui" -execdir gtk4-builder-tool simplify --3to4 --replace {} \;
  

• Convert to new list widget