Remove worker_replication_* settings (#15491)

* Add master to the instance_map as part of Complement, have ReplicationEndpoint look at instance_map for master.

* Fix typo in drive by.

* Remove unnecessary worker_replication_* bits from unit tests and add master to instance_map(hopefully in the right place)

* Several updates:

1. Switch from master to main for naming the main process in the instance_map. Add useful constants for easier adjustment of names in the future.
2. Add backwards compatibility for worker_replication_* to allow time to transition to new style. Make sure to prioritize declaring main directly on the instance_map.
3. Clean up old comments/commented out code.
4. Adjust unit tests to match with new code.
5. Adjust Complement setup infrastructure to only add main to the instance_map if workers are used and remove now unused options from the worker.yaml template.

* Initial Docs upload

* Changelog

* Missed some commented out code that can go now

* Remove TODO comment that no longer holds true.

* Fix links in docs

* More docs

* Remove debug logging

* Apply suggestions from code review

Co-authored-by: reivilibre <olivier@librepush.net>

* Apply suggestions from code review

Co-authored-by: reivilibre <olivier@librepush.net>

* Update version to latest, include completeish before/after examples in upgrade notes.

* Fix up and docs too

---------

Co-authored-by: reivilibre <olivier@librepush.net>

tests/module_api/test_api.py

@@ -837,6 +837,7 @@ class ModuleApiWorkerTestCase(BaseModuleApiTestCase, BaseMultiWorkerStreamTestCa
         conf = super().default_config()
         conf["stream_writers"] = {"presence": ["presence_writer"]}
         conf["instance_map"] = {
+            "main": {"host": "testserv", "port": 8765},
             "presence_writer": {"host": "testserv", "port": 1001},
         }
         return conf