Problem:
nvim_get_autocmds cannot filter by id.

Solution:
Support it.

Problem: Right aligned virtual text can cover up buffer text if virtual
text is too long

Solution: An additional option for `virt_text_pos` called
`eol_right_align` has been added to truncate virtual text if it would
have otherwise covered up buffer text. This ensures the virtual text
extends no further left than EOL.

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.

feat(extmark): stack multiple highlight groups in `hl_group`

This has been possible in the "backend" for a while but
API was missing.

Followup: we will need a `details2=true` mode for `nvim_get_hl_id_by_name`
to return information in a way forward compatible with even further
enhancements.

This was kept for a while as it was a useful short hand and initially
matched what highlights what actually properly implemented. But now
|vim.hl.range()| is a better high-level shorthand with full support for
native multi-line ranges.

Problem:  Anchoring a floating window to the tabline and laststatus is
          cumbersome; requiring autocommands and looping over all
          windows/tabpages.
Solution: Add new "tabline" and "laststatus" options to the `relative`
          field of nvim_open_win() to place a window relative to.

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`.