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/extensions_ui/src/extension_suggest.rs

@@ -29,6 +29,7 @@ pub fn suggested_extension(file_extension_or_name: &str) -> Option<Arc<str>> {
                 ("git-firefly", "MERGE_MSG"),
                 ("git-firefly", "NOTES_EDITMSG"),
                 ("git-firefly", "TAG_EDITMSG"),
+                ("gleam", "gleam"),
                 ("graphql", "gql"),
                 ("graphql", "graphql"),
                 ("java", "java"),
@@ -39,6 +40,7 @@ pub fn suggested_extension(file_extension_or_name: &str) -> Option<Arc<str>> {
                 ("r", "r"),
                 ("r", "R"),
                 ("sql", "sql"),
+                ("svelte", "svelte"),
                 ("swift", "swift"),
                 ("templ", "templ"),
                 ("wgsl", "wgsl"),