ChecksMate: implement new game

[chesslogic]

What is this fixing or adding?

ChecksMate is a client for Chess played against a computer-controlled engine. Unique features include pocket pieces, fairy pieces, and random starting positions.

The client is available here: https://github.com/chesslogic/chessv

How was this tested?

Initial testing

When putting this up for draft, the Archipelago community had never played this in any Unsupported multiworld hosted on the Discord server.

Some automated tests are available in the repository regarding some specific settings.

The author has played ChecksMate in 2 "mid-sized" multiworlds (6-15 games), 1 "large-ish" multiworld (30-40 games), and one or two dozen XS multiworlds (2-5 games). The non-XS multiworlds were async, and the XS multiworlds were sync.

Many of these multiworlds involved multiple copies of ChecksMate. ChecksFinder was common to many XS multiworlds.

Community testing

Since then, in addition to recurring off-server multiworlds, Archipelago players from the Discord have participated in 2 multiworlds involving over 50% copies of ChecksMate as well as dozens of asyncs accepting unsupported apworlds. Even players new to chess have been able to successfully complete their game on sufficiently relaxed settings.

The automated tests have been further honed.

If this makes graphical changes, please attach screenshots.

Please be advised that no ChecksMate client is expected to be added to the Archipelago repository. The author provides releases of a ChecksMate client on GitHub, but the client specification may also be implemented by other Chess tools supporting arbitrary fairy chess formats.

The following images have descriptive alt text.

[Silvris]

A couple of major things, mostly needing to swap to the options API when 0.4.4 releases as that will greatly reduce the complexity of this PR.

[chesslogic]

Thanks for the review. The comments helped me a lot with style and even performance, and I continue to appreciate your advice.

I expect to leave this in draft until the game is involved in an Unsupported multiworld on the Discord, at which point I will be glad to receive a thorough review.