Add an input for uploading test logs

[andyholmes]

Add inputs to action.yml for:

• upload-test-logs
• upload-test-includes

If upload-test-logs is true, add --keep-build_dirs to the flatpak-builder arguments. Try to detect whether known logs paths are present (e.g. $builddir/meson-logs) and use them as a default for upload-test-includes.

If upload-test-includes is given, override any defaults set by upload-test-logs and upload the provided paths as an artifact.