Updates Sir-lancebot To Python3.9.4

[Shivansh-007]

Closes #549

This PR upgrades the Python version we use for the bot to Python 3.9.4. One of the major upgrades this offers for us is that we can now use list[dict[str, str]] rather than importing typing module and then doing those ugly typing.List[Typing.Dict[str, str]] annotations.

Changes to be aware of

• Bumps Python to 3.9 in Pipfile & lock and Docker.

• Bumps all dependencies to the latest version, which support python3.9 and solve the breaking changes only

• Adds super class call to LinePaginator, discord.py adds linesep argument to the Paginator in v1.7.0.

• typing module has deprecated Iterator, Mapping, Callable, Container in python3.9, and they have to be imported from collections.abc rather now.

• asyncio.ensure_future has been changed to asyncio.create_task as it​ is a higher level function and is more readable, and preferred over ​asyncio.ensure_future​

• loop.run_in_executor has been changed to asyncio.to_thread. It is mainly used for running IO-bound functions in a separate thread to avoid blocking the event loop, and essentially works as a high-level version of run_in_executor() that can directly take keyword arguments.

Dependency Tracker

[REMOVED] All dependencies have been tested and updated by myself and @ToxicKidz

[Shivansh-007]

Merged python-discord/sir-lancebot:main into the PR branch to make the PR up to date with all the changes, the merge introduces no breaking change.

[HassanAbouelela]

Preliminary block on this PR (I have not reviewed the actual content yet). This PR can not be merged yet, for the same reason our other projects can not be migrated. A lot of the dependencies you've bumped do not have wheels for 3.9 yet, which means these changes are not acceptable through no fault of your own. Without wheels, you need build tools, which significantly hurts people contributing on systems that don't have them by default (such as windows), and will not work in our CI. You can test the state of these current deps using the docker image.

[Shivansh-007]

A lot of the dependencies you've bumped do not have wheels for 3.9 yet

This is not entirely correct, I tested it on docker and with pipenv, the only dependency which doesn't have python3.9 wheels is pycares.

[Xithrius]

Way too many conflicts. Best to make a new PR.