* Rename scripts-dev to have suffices

* Update references to `scripts-dev`

* Changelog

* These scripts don't pass mypy

* Labeled a lot more code blocks with the appropriate type
* Fixed a couple of minor typos (missing/extraneous commas)

Signed-off-by: Sumner Evans <me@sumnerevans.com>

`room_invite_state_types` was inconvenient as a configuration setting, because
anyone that ever set it would not receive any new types that were added to the
defaults. Here, we deprecate the old setting, and replace it with a couple of
new settings under `room_prejoin_state`.

 - Update black version to the latest
 - Run black auto formatting over the codebase
    - Run autoformatting according to [`docs/code_style.md
`](https://github.com/matrix-org/synapse/blob/80d6dc9783aa80886a133756028984dbf8920168/docs/code_style.md)
 - Update `code_style.md` docs around installing black to use the correct version

https://github.com/matrix-org/synapse/tree/develop/docs/sphinx doesn't seem to really be utilised or changed recently since the initial commit. I like the idea of exportable documentation of the codebase, but at the moment after running through the build instructions the generated website wasn't very useful...

Ensure good comprehension hygiene using flake8-comprehensions.

I want to do some key rotation, and it is silly that we don't have a way to do
this.

Converting some of the rst documentation to markdown.  Attempted to
preserve whitespace and line breaks to minimize cosmetic change.