Save all properties from Preferences UI as actual preferences

Previously some of them were saved only for current .blend file, moving them to preferences will make it more consistent with usual Blender UX. If needed we'll be able to add some way to fine-grain them later.

There's also a temporary patch that's going to migrate old .blend-props to new preferences-props to make process less disruptive.

src/bonsai/test/tool/test_debug.py

@@ -55,8 +55,8 @@ class TestLoadExpress(NewFile):
 
 class TestPurgeHdf5Cache(NewFile):
     def test_run(self):
-        props = tool.Blender.get_bim_props()
-        cache_dir = Path(props.cache_dir)
+        prefs = tool.Blender.get_addon_preferences()
+        cache_dir = Path(prefs.cache_dir)
         test_file = cache_dir / "test.h5"
         test_file.parent.mkdir(parents=True, exist_ok=True)
         test_file.touch()