This makes a few major changes:
- cursor style on terminal is single source of stylistic truth
- cursor style is split between style and style request
- cursor blinking is handled by the renderer thread
- cursor style/visibility is no longer stored as persistent state on
renderers
- cursor style computation is extracted to be shared by all renderers
- mode 12 "cursor_blinking" is now source of truth on whether blinking
is enabled or not
- CSI q and mode 12 are synced like xterm
