Release from the version in project.godot

The version now lives in project.godot (application/config/version)
and Settings.version reads it from there. The Build workflow tests and
exports on every push, and on main creates the tag, uploads the builds
and creates the Gitea release when that version has no tag yet. This
replaces gitea-release.yaml, which released when a branch named after
the version was pushed.

Godot setup moves into a local .gitea/actions/setup-godot action shared
by the test and build jobs, and Godot is updated to 4.7.2 to match the
editor the project is made with.

tests/unit/test_settings.gd

@@ -0,0 +1,13 @@
+extends GdUnitTestSuite
+
+
+func test_version_comes_from_project_settings() -> void:
+    assert_str(Settings.version).is_equal(
+            ProjectSettings.get_setting("application/config/version"))
+
+
+func test_version_is_major_minor_patch() -> void:
+    # The release job tags and names builds with this version
+    var pattern: RegEx = RegEx.create_from_string("^\\d+\\.\\d+\\.\\d+$")
+
+    assert_object(pattern.search(Settings.version)).is_not_null()