Implement (Contour's) Color Palette Update Notification and report

[Yaraslaut]

Description of the new feature

Implement Dark and Light Mode detection protocol adopted by few terminals and apps (neovim being the most well known i guess) the specification is presented here: https://github.com/contour-terminal/contour/blob/master/docs/vt-extensions/color-palette-update-notifications.md

Proposed technical implementation details

No response

[j4james]

This might also be a potential solution for #10639 (not so much the dark/light mode detection, but the ability to request palette update notifications).