Rust: Vendor 3rdparty dependencies.

We've been observing some performance issues using crate_universe on CI.
Therefore, we're moving to vendor the auto-generated BUILD files
in our repository. This should provide a nice speed boost, while
getting rid of the complexity of the "rust cache" job we've been using
when we had a lot of git dependencies.

This PR includes a vendor script, and I'll put up a CI job internally
that runs that vendor script on Cargo.toml and Cargo.lock changes, to check
that the vendored files are in sync.

ruby/extractor/BUILD.bazel

@@ -1,5 +1,7 @@
-load("@tree_sitter_extractors_deps//:defs.bzl", "aliases", "all_crate_deps")
 load("//misc/bazel:rust.bzl", "codeql_rust_binary")
+load("//misc/bazel/3rdparty/tree_sitter_extractors_deps:defs.bzl", "aliases", "all_crate_deps")
+
+exports_files(["Cargo.toml"])
 
 codeql_rust_binary(
     name = "extractor",

ruby/extractor/Cargo.toml

@@ -5,6 +5,7 @@ version = "0.1.0"
 authors = ["GitHub"]
 edition = "2021"
 
+# When updating these dependencies, run `misc/bazel/3rdparty/update_cargo_deps.sh`
 [dependencies]
 tree-sitter = ">= 0.23.0"
 tree-sitter-embedded-template = "0.23.2"