The official developer documentation in in :h dev-lua-doc specifies to
use "--@" for special/magic tokens. However, this format is not
consistent with EmmyLua notation (used by some Lua language servers) nor
with the C version of the magic docstring tokens which use three comment
characters.

Further, the code base is currently split between usage of "--@",
"---@", and "--- @". In an effort to remain consistent, change all Lua
magic tokens to use "---@" and update the developer documentation
accordingly.

These numbers are guaranteed to be stable even if you do "highlight
clear" (all attributes disappear, but not the id to name mapping itself)

This changes the behavior of the hl_cache to the old one.

- when the capture exists as a hlgroup -> use it
- when hl_map contains a mapping -> use it
- else do nothing (before: map capture to non-existing capture)

Before also captures `@foo.bar` would intend to use the hlgroup `foo.bar`
which results in a confusing error since hlgroups can't contain dots.

For the case of Clojure and other Lisp syntax highlighting, it is
necessary to create huge regexps consisting of hundreds of symbols with
the pipe (|) character. To make things more difficult, these Lisp
symbols sometimes consists of special characters that are themselves
part of special regexp characters like '*'. In addition to being
difficult to maintain, it's performance is suboptimal.

This patch introduces a new predicate to perform 'source' matching in
amortized constant time. This is accomplished by compiling a hash table
on the first use.

[RDY] tree-sitter ensure there is a nested table allocated for `#set!`