fix(neovim): floating windows can now have statuslines

[perrin4869]

This pull request is necessary due to recent changes in Neovim nightly which introduced native support for statuslines on floating windows (e.g., neovim/neovim#36521). I could observe statuslines being drawn on telescope prompts and notify.nvim prompts in nightly due to that commit.

It is now not reliable to check for nvim_win_get_config(0).focusable at all, because floating windows are focusable by default, and that will cause the statusline to be drawn under them.
Also, we need to check for skippability of windows before calling setwinvar(n, '&statusline', s[n!=w]) to prevent a statusline being drawn on floating windows that are not in focus, so I added an optional winid variable to the s:skip function.

[perrin4869]

I guess another approach would be to use the existing nvim api to filter out floating windows, similar to: https://github.com/carbon-steel/detour.nvim/blob/204f61e64f87c7c6fd4ef4a387631c9a9efc2573/lua/detour/util.lua#L85