extension_host: Add npm:install capability (#35144)

This PR adds a new `npm:install` capability for installing npm packges
in extensions.

Currently all npm packages are allowed.

Release Notes:

- N/A

crates/extension_host/src/wasm_host/wit/since_v0_6_0.rs

@@ -745,6 +745,9 @@ impl nodejs::Host for WasmState {
         package_name: String,
         version: String,
     ) -> wasmtime::Result<Result<(), String>> {
+        self.capability_granter
+            .grant_npm_install_package(&package_name)?;
+
         self.host
             .node_runtime
             .npm_install_packages(&self.work_dir(), &[(&package_name, &version)])