Migrate tree-sitter support to MODULE.bazel

[jonmeow]

The WORKSPACE file is deprecated; support is already off by default, and it'll be removed in the next major bazel release. Our main dependency is tree-sitter, and I'm trying to address that here.

We're currently using https://github.com/elliottt/rules_tree_sitter, but that hasn't been updated in a couple years, meaning it lacks MODULE.bazel support. In the registry, there's https://registry.bazel.build/modules/tree-sitter-bazel, but this is only the parser libraries of tree-sitter, not the generator. I'm using it for that much, at least.

For the generator, which transforms grammar.js to parser.c/h, I'm just requiring a non-hermetic invocation (i.e., people who want to work on it will need to install tree-sitter; see the README.md updates). I tried running it manually, but parser.c is about 600 KB; pre-commit rejects files that large and I don't think an exception makes sense to override for this (it'd probably also grow substantially if the grammar were updated to cover more syntax). In order to make the non-hermetic call not break "bazel build //..." for most developers, I'm marking most targets in the package as manual.

Note, I did look long and hard at using aspect_rules_js/rules_nodejs to invoke npm. This took a lot of time, and I have a commit that's mostly working, except I hit a point where it uses declare_symlink which we disallow for compatibility reasons (commit "Lots of work for figuring out rule_js uses declare_symlink" on the PR). As a consequence, I think we can't use the primary supported ways to have hermetic npm calls.

Also, treesitter -> tree_sitter because it's generally called tree-sitter, two words. We even had a treesitter/src/tree_sitter directory so it's a bit inconsistent.

As far as bugs here, the parser library breaks bazel queries, e.g. the error:

ERROR: Evaluation of query "somepath(//..., @llvm-project//third-party/unittest:gtest)" failed: preloading transitive closure failed: no such package '@@[unknown repo 'platforms' requested from @@tree-sitter-bazel+]//': The repository '@@[unknown repo 'platforms' requested from @@tree-sitter-bazel+]' could not be resolved: No repository visible as '@platforms' from repository '@@tree-sitter-bazel+'

I'm just excluding tree_sitter from queries where I can to work around the error.

[jonmeow]

Note I split out the woff2 removal to #4781; this depends on it to remove the WORKSPACE file