add slots in all classes

[adbar]

Type of pull request:

• Bug fix
• Feature
• Other

Description:

Since we're at it I thought we could add slots in all classes (the TypedDict classes are not concerned).

Related Issues:

See discussion in PR #1075.

Checklist:

• I have read and followed the contribution guidelines.
• I have added necessary documentation (if applicable).
• The changes pass all existing tests.

[MarkZH]

I'm reluctant to merge this. The documentation indicates that slots are purely for performance optimization and lichess-bot isn't a bottleneck. All lichess-bot does is act as a translator for messages between lichess.org and chess bots. This change may save microseconds, but lichess-bot is always waiting at least tens or hundreds of milliseconds for network traffic and bot calculations. In fact, most of the computation lichess-bot does is handled by the python-chess library, which doesn't use slots anywhere.

@AttackingOrDefending, any comments?

[AttackingOrDefending]

I would also prefer not adding __slots__, as they make the code less readable in my opinion. #1069 was merged as it made some readability changes (e.g. changing elif to if) and improved the speed without loss in the readability of that code.

[adbar]

OK, I understand.