[V3] Optimize the backup command (#1666)

* [V3 Core] Enhance [p]backup to exclude some files

* Backup the repo list too

* Lol Sinbad's pre-commit hook

* Add option of sending the backup to the owner via DM

* Drop an unnecessary config object in RepoManager

* Move the backup functionality in redbot-setup to the new stuff

* More work on implementation, including backing up the instance data

tests/cogs/downloader/test_downloader.py

@@ -33,9 +33,8 @@ def patch_relative_to(monkeysession):
 
 
 @pytest.fixture
-def repo_manager(tmpdir_factory, config):
-    config.register_global(repos={})
-    rm = RepoManager(config)
+def repo_manager(tmpdir_factory):
+    rm = RepoManager()
     # rm.repos_folder = Path(str(tmpdir_factory.getbasetemp())) / 'repos'
     return rm