Make install procedure overwrite existing addons

However, back them up first and restore them if anything goes wrong

bpkg_manager/__init__.py

@@ -195,8 +195,10 @@ class BPKG_OT_install(SubprocMixin, bpy.types.Operator):
         install_path = pathlib.Path(bpy.utils.user_resource('SCRIPTS', 'addons', create=True))
         self.log.debug("Using %s as install path", install_path)
 
+        import addon_utils
+
         proc = multiprocessing.Process(target=subproc.download_and_install,
-                                       args=(self.pipe_subproc, self.package_url, install_path))
+                                       args=(self.pipe_subproc, self.package_url, install_path, addon_utils.paths()))
         return proc
 
     def _subproc_progress(self, progress: subproc.Progress):