bd808's move all the things refactoring and fixup MR

[x] Move all python code into a module (src/wikibugs2)
[x] Create a top level entrypoint at wikibugs2.__main__ so that it can be executed as python3 -m wikibugs2 ...
[x] Move the entrypoint of grrrrit.py to python3 -m wikibugs2 gerrit
[x] Move the entrypoint of wikibugs.py to python3 -m wikibugs2 phorge
[x] Move the entrypoint of redis2irc.py to python3 -m wikibugs2 irc
[x] Move the entrypoint of tools/update_contributors.py to python3 -m wikibugs2 update-credits
[x] Remove manage.py script
[x] Remove log_to_irc.py script
[x] Remove tools/test_tags.py script
[x] Convert config.json / configfetcher.py configuration system to envvars
[x] Introduce common Python linters & black for code formatting
[x] Update k8s-jobs.yaml for new entrypoints
[x] Convert gerrit ssh key to envvar setting

Bug: T358775
Bug: T357851