fix(language-service): implement realpath to resolve symlinks (#40593)

The `LanguageServiceAdapter` must implement `realpath` in order to resolve
symlinks in `node_modules`.

Local libraries are often symlinked in `node_modules` by adding a local
dependency in `package.json`.

Fix https://github.com/angular/vscode-ng-language-service/issues/1083

PR Close #40593

packages/language-service/ivy/adapters.ts

@@ -51,6 +51,14 @@ export class LanguageServiceAdapter implements NgCompilerAdapter {
     return this.project.projectService.toCanonicalFileName(fileName);
   }
 
+  /**
+   * Return the real path of a symlink. This method is required in order to
+   * resolve symlinks in node_modules.
+   */
+  realpath(path: string): string {
+    return this.project.realpath?.(path) ?? path;
+  }
+
   /**
    * readResource() is an Angular-specific method for reading files that are not
    * managed by the TS compiler host, namely templates and stylesheets.