Fixes #20139

Use the first, not last, query for a language on runtimepath. Typically,
this implies that a user query will override a site plugin query, which 
will override a bundled runtime query.

Problem: Treesitter queries for a given language in runtime were merged together, 
leading to errors if they targeted different parser versions (e.g., bundled viml queries 
and those shipped by nvim-treesitter).
Solution:  Runtime queries now work as follows:
* The last query in the rtp without `; extends` in the header will be used as the base query
* All queries (without a specific order) with `; extends` are concatenated with the base query

BREAKING CHANGE: queries need to be updated if they are meant to extend other queries

feat(treesitter): use weak tables when possible

Also add the defaulttable function to create a table whose values are created when a key is missing.

- Added 'spell' option to extmarks:

  Extmarks with this set will have the region spellchecked.

- Added 'noplainbuffer' option to 'spelloptions':

  This is used to tell Neovim not to spellcheck the buffer. The old
  behaviour was to spell check the whole buffer unless :syntax was set.

- Added spelling support to the treesitter highlighter:

  @spell captures in highlights.scm are used to define regions which
  should be spell checked.

- Added support for navigating spell errors for extmarks:

  Works for both ephemeral and static extmarks

- Added '_on_spell_nav' callback for decoration providers:

  Since ephemeral callbacks are only drawn for the visible screen,
  providers must implement this callback to instruct Neovim which
  regions in the buffer need can be spell checked.

  The callback takes a start position and an end position.

  Note: this callback is subject to change hence the _ prefix.

- Added spell captures for built-in support languages

Co-authored-by: Lewis Russell <lewis6991@gmail.com>
Co-authored-by: Björn Linse <bjorn.linse@gmail.com>

This removes the support for defining links via
vim.treesitter.highlighter.hl_map (never documented, but plugins did
anyway), or the uppercase-only `@FooGroup.Bar` to `FooGroup` rule.

The fallback is now strictly `@foo.bar.lang` to `@foo.bar` to `@foo`,
and casing is irrelevant (as it already was outside of treesitter)

For compatibility, define default links to builting syntax groups
as defined by pre-existing color schemes

The private 'get_node_range' function from the languagetree module has
been renamed and remains private as it serve a purpose that is only
relevant inside the languagetree module.

The 'get_node_range' upstreamed from nvim-treesitter in the treesitter
module has been made public as it is in itself a utlity function.

As part of the upstream of utility functions from nvim-treesitter, this
option when set to false allows to return a table (downstream behavior).
Effectively making the switch from the downstream to the upstream
function much easier.