Remove use of settings.register, not part of the public API

[FireChickenProductivity]

settings.register is not part of the public API and has performance implications, so its use is discouraged. We only use this for the draft window and a snippet.

I recommend removing the snippet.

The draft window DraftManager can just update the styling when the draft window is shown, and we can update settings.talon.example and possibly the setting descriptions to explain that seeing the results of changing those settings requires redrawing the window with a command.

[nriley]

From the Community Backlog session — we discussed that since the contents of the draft window persists between "draft hide"/"draft show" and we can also redefine draft show to update the window appearance from settings, that we can remove settings.register entirely.