Add type annotations

[V02460]

This PR adds a lot of type annotations to the code. As this alone made the type checker not happy, additionally some smaller changes were made:

• Replace Telegram-related star imports to be more linter-friendly
• Fix some return statements
• Use different variable names when it’s using different types (e.g. in this method with the puppet variable changed to dbpuppet)
• Added some basic NewTypes (MatrixUserId, MatrixRoomId, MatrixEventId, TelegramId, MatrixEvent)
• Add an error enum to puppet.py to replace int error values
• Changed Context to return a type safe tuple via a property

This PR does not address all the Optional discrepancies as a lot of possibly-None variables are currently accessed. Fixing this is not as easy as the rest as it is heavily related to execution logic and error handling, but I might do some smaller PRs regarding these.

For typechecking I used mypy and disabled the checking for errors with Optional. Sadly, I did only check for python 3.7 as mypy does not handle the future-fstrings in 3.5 well. This is the configuration I used:

python3 -m mypy <file> --ignore-missing-imports --no-implicit-optional --no-strict-optional --follow-imports silent`

I did test the changes on my server and it survived real-world usage of a few persons.

[tulir]

Thanks!

The changes mostly look good, but there are two style things to change:

• Use the Go initialism capitalization convention. Basically just s/Id/ID/g for the new types.
• Use double quotes instead of single quotes for strings.

I also just noticed that neither of those details are documented/configured anywhere, so sorry about that.