Some plugins (*cough* kak-lsp) and help texts tend to have immensely long content
in a single line. This generates info boxes that span the entire terminal width.
This is made especially worse on widescreen monitors or at small text size.
This grants user control over how wide these boxes are.
I deliberately avoid pushing this change to `kak-lsp` because it's not the only
plugin that this could help--see the `hook` help text for an example of this
problem in vanilla Kakoune. I would also suggest that since this is a rendering
concern, it be handled by the terminal rendering logic.
Enable it if supported by default, let the user override it with
the existing terminal_synchronized ui option.
This should finalize work discussed on #4317
Synchronized output does not work well with various terminals
(including the linux console). It should also be unnecessary when
not going through a slow link.
This will eventually be removed if it is not proven to be useful
to some users.
This should reduce flicker, by avoiding transient states where
info/menu windows are not displayed, and paves the way for proper
diffing of the screen.
