Follow-up to #27358.

Problem:
nvim_get_autocmds cannot filter by id.

Solution:
Support it.

Problem:  Combined highlighting was not applied to nvim_eval_statusline(),
          and 'statuscolumn' sign segment/numhl highlights.
Solution: Add an additional `groups` element to the return value of
          `nvim_eval_statusline()->highlights`. This is an array of stacked
          highlight groups (highest priority last). Also resolve combined
          highlights for the 'statuscolumn' sign segment/numhl highlights.
          Expose/synchronize some drawline.c logic that is now mimicked in
          three different places.

fix(wininfo): when freeing windows, free the lowest priority wininfo

Problem:  Metadata may be revised for end mark of a revalidated pair.
Solution: Revise metadata for start mark of a revalidated pair.

On master (and also before #31539) closing a window could cause the
used wininfo for a buffer to change. This is due to always removing the
previous NULL wininfo when deleting a window, even if that wininfo had
higher priority than the the deleted window's own wininfo.

Instead delete the wininfo with lowest priority. This retains the memory
saving efect while not affecting the effective value of window options
and so on.

Problem:
The `nvim_notify` API (note: unrelated to `vim.notify()` Lua API) was
not given any real motivation in https://github.com/neovim/neovim/pull/13843

There are, and were, idiomatic and ergonomic alternatives already.

Solution:
Deprecate `nvim_notify`.

Problem:  We want to deprecate `nvim_err_write(ln)()` but there is no
          obvious replacement (from Lua). Meanwhile we already have
          `nvim_echo()` with an `opts` argument.
Solution: Add `err` argument to `nvim_echo()` that directly maps to
          `:echoerr`.