Generate tree-sitter parsers if they don't exist in git repo

[slinlee]

The problem is that the grammar .gitignores the src/ directory (see here). Helix's build process for grammars currently requires the generated src/ directory which is all the C/C++ files you need to compile the parser.

Originally posted by @the-mikedavis in #1853 (comment)

[the-mikedavis]

tree-sitter/tree-sitter#1641 has some info on how nvim-treesitter deals with grammars. They have a system simliar to ours where the repositories are cloned and in some cases, the src files get generated by calling out to tree-sitter and sometimes even npm. I've been thinking about how to solve some of those issues and I think a central registry which packages the generated src directories is a reasonable increment, so that's what I've been tinkering with in helix-editor/tspm. The idea there is that you can package the grammars into a minimal and reproducible tarball with a uniform structure, so all of the packaging concerns like getting dependencies (submodules, npm, etc.), generating the src files and specifying the ABI live in TSPM instead of editors / tree-sitter consumers. Then consumers download and extract the tarball and compile the C files.

That doesn't solve all of the issues there (in particular around safety), but I think it's a good middle-ground between the current state and the ideal eventual state (see the "Native Library, WASM parsers" part of tree-sitter/tree-sitter#930).

[the-mikedavis]

We could do this either by embedding tree-sitter-cli or shelling out to it. I think both options are less favorable to me than #1970, though, so closing out in favor of that.