Problem:  diff feature can be improved
Solution: include the linematch diff alignment algorithm
          (Jonathon)

closes: vim/vim#9661

https://github.com/vim/vim/commit/7c7a4e6d1ad50d5b25b42aa2d5a33a8d04a4cc8a

Co-authored-by: Jonathon <jonathonwhite@protonmail.com>

Problem:  Cannot control cursor positioning of getchar().
Solution: Add "cursor" flag to {opts}, with possible values "hide",
          "keep" and "msg".

related: vim/vim#10603
closes: vim/vim#16569

https://github.com/vim/vim/commit/edf0f7db28f87611368e158210e58ed30f673098

Problem:  getchar() can't distinguish between C-I and Tab.
Solution: Add {opts} to pass extra flags to getchar() and getcharstr(),
          with "number" and "simplify" keys.

related: vim/vim#10603
closes: vim/vim#16554

https://github.com/vim/vim/commit/e0a2ab397fd13a71efec85b017d5d4d62baf7f63

Cherry-pick tv_dict_has_key() from patch 8.2.4683.

Problem:  Vim doesn't highlight to be inserted text when completing
Solution: Add support for the "preinsert" 'completeopt' value
          (glepnir)

Support automatically inserting the currently selected candidate word
that does not belong to the latter part of the leader.

fixes: vim/vim#3433
closes: vim/vim#16403

https://github.com/vim/vim/commit/edd4ac3e895ce16034c7e098f1d68e0155d97886

Co-authored-by: glepnir <glephunter@gmail.com>

Problem:
nvim_get_autocmds cannot filter by id.

Solution:
Support it.

Problem:  insert-completed items are always sorted, although the LSP
          spec[1] standard defines sortText in the returned
          completionitem list. This means that the server has sorted the
          results. When fuzzy is enabled, this will break the server's
          sorting results.
Solution: disable sorting of candidates when "nosort" is set in
          'completeopt'

[1]
https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#completionItem

closes: vim/vim#16501

https://github.com/vim/vim/commit/f400a0cc41113eb75516bdd7f38aeaa15208ba2c

Co-authored-by: glepnir <glephunter@gmail.com>

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`