Fix issues with extension API that come up when moving Svelte into an extension (#9611)

We're doing it. Svelte support is moving into an extension. This PR
fixes some issues that came up along the way.

Notes

* extensions need to be able to retrieve the path the `node` binary
installed by Zed
* previously we were silently swallowing any errors that occurred while
loading a grammar
* npm commands ran by extensions weren't run in the right directory
* Tree-sitter's WASM stdlib didn't support a C function (`strncmp`)
needed by the Svelte parser's external scanner
* the way that LSP installation status was reported was unnecessarily
complex

Release Notes:

- Removed built-in support for the Svelte and Gleam languages, because
full support for those languages is now available via extensions. These
extensions will be suggested for download when you open a `.svelte` or
`.gleam` file.

---------

Co-authored-by: Marshall <marshall@zed.dev>

crates/languages/Cargo.toml

@@ -49,7 +49,6 @@ tree-sitter-elixir.workspace = true
 tree-sitter-elm.workspace = true
 tree-sitter-embedded-template.workspace = true
 tree-sitter-erlang.workspace = true
-tree-sitter-gleam.workspace = true
 tree-sitter-glsl.workspace = true
 tree-sitter-go.workspace = true
 tree-sitter-gomod.workspace = true
@@ -75,7 +74,6 @@ tree-sitter-regex.workspace = true
 tree-sitter-ruby.workspace = true
 tree-sitter-rust.workspace = true
 tree-sitter-scheme.workspace = true
-tree-sitter-svelte.workspace = true
 tree-sitter-toml.workspace = true
 tree-sitter-typescript.workspace = true
 tree-sitter-vue.workspace = true