Monochrome Rich traceback rendering w/ ConsoleRenderer(colors=False) (#794)

* RichTracebackFormatter: Extends type annotation to allow no monochrome output

The None isn't specified as Literal, b/c ruff tells us how to express this.

* ConsoleRenderer: When colors=False, set monochrome output for RichTracebackFormatter

* Use ternary & use identity to detect defaults

* Test switching back to colors

* Docs and changelogs

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Co-authored-by: Hynek Schlawack <hs@ox.cx>