cmd/compile: add a dark mode to ssa html generation which can be toggled
cmd/compile: add a dark mode to ssa html generation which can be toggled

add a tag that when clicked, toggles a dark mode. It keeps intact
the grayed out dead values/blocks, all the highlight colors, and ensures
text is always readable.

Fixes #34325

Change-Id: I4af1e4b5f4a5b63e54c992e90f8474cc51c63465
Reviewed-on: https://go-review.googlesource.com/c/go/+/220260
Reviewed-by: Josh Bleecher Snyder <cdc248cc4d32e4fbfe04e45228163bcecd48a0b9@gmail.com>
Run-TryBot: Josh Bleecher Snyder <cdc248cc4d32e4fbfe04e45228163bcecd48a0b9@gmail.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

akutz/go,golang/go,CAFxX/go,nawawi/go,nawawi/go,akutz/go,nawawi/go,akutz/go,golang/go,CAFxX/go,golang/go,cloudflare/go,cloudflare/go,CAFxX/go,nawawi/go,cloudflare/go,akutz/go,akutz/go,golang/go,golang/go,CAFxX/go,cloudflare/go,akutz/go,akutz/go,nawawi/go,nawawi/go,golang/go,cloudflare/go,CAFxX/go,CAFxX/go,akutz/go,CAFxX/go,cloudflare/go,nawawi/go,nawawi/go,cloudflare/go,CAFxX/go,cloudflare/go,golang/go,golang/go