Updates the git connection dialog to reflect default agentic behavior,
followed by default keys and only then reverting to a custom selection
if the user desires
Fixes https://gitlab.com/kicad/code/kicad/-/issues/20204
- Utilize scoped deletion for individual git_*_free() calls
- Protect against multiple usage when updating icons
- Reduce frequency of git update calls
Push the git checks from the main thread into child threads to prevent
resource contention in some cases where Windows machines might have many
files in git that are _also_ being managed by Google Drive
Fixes https://gitlab.com/kicad/code/kicad/-/issues/20078
Don't keep passwords in plain text config files that may be checked into
version control. Passwords stored in system-specific password managers
Fixes https://gitlab.com/kicad/code/kicad/-/issues/18053
Recommendation is to avoid using the year nomenclature as this
information is already encoded in the git repo. Avoids needing to
repeatly update.
Also updates AUTHORS.txt from current repo with contributor names
