Now `:InspectTree` will show missing nodes as e.g. `(MISSING identifier)`
or `(MISSING ";")` rather than just `(identifier)` or `";"`. This is
doable because the `MISSING` keyword is now valid query syntax.

Co-authored-by: Christian Clason <c.clason@uni-graz.at>

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

When given, only that range will be checked for validity rather than the
entire tree. This is used in the highlighter to save CPU cycles since we
only need to parse a certain region at a time anyway.

This means that all work previously done by a `_parse()` iteration will
be kept in future iterations. This prevents it from running indefinitely
in some cases where the file is very large and there are 2+ injections.

Problem:
When running an initial parse, parse() returns an empty table rather
than an actual range. In `languagetree.lua`, we manually check if
a parse was incremental to determine the changed parse region.

Solution:
- Always return a range (in the C side) from parse().
- Simplify the language tree code a bit.
- Logger no longer shows empty ranges on the initial parse.