This commit also marks `child_containing_descendant()` as deprecated
(per upstream's documentation), and uses `child_with_descendant()` in
its place. Minimum required tree-sitter version will now be `0.24`.
**Problem:** The documentation for `TSNode` and `TSTree` methods is
incomplete from the LSP perspective. This is because they are written
directly to the vimdoc, rather than in Lua and generated to vimdoc.
**Solution:** Migrate the docs to Lua and generate them into the vimdoc.
This requires breaking up the `treesitter/_meta.lua` file into a
directory with a few different modules.
This commit also makes the vimdoc generator slightly more robust with
regard to sections that have multiple help tags (e.g. `*one* *two*`)
