feat(language-service): implement signature help (#41581)

This commit implements signature help in the Language Service, on top of
TypeScript's implementation within the TCB.

A separate PR adds support for translation of signature help data from TS'
API to the LSP in the Language Service extension.

PR Close #41581

packages/compiler-cli/src/ngtsc/perf/src/api.ts

@@ -144,6 +144,11 @@ export enum PerfPhase {
    */
   LsComponentLocations,
 
+  /**
+   * Time spent by the Angular Language Service calculating signature help.
+   */
+  LsSignatureHelp,
+
   /**
    * Tracks the number of `PerfPhase`s, and must appear at the end of the list.
    */

packages/compiler-cli/src/ngtsc/typecheck/src/expression.ts

@@ -69,7 +69,9 @@ class AstTranslator implements AstVisitor {
 
     // The `EmptyExpr` doesn't have a dedicated method on `AstVisitor`, so it's special cased here.
     if (ast instanceof EmptyExpr) {
-      return UNDEFINED;
+      const res = ts.factory.createIdentifier('undefined');
+      addParseSpanInfo(res, ast.sourceSpan);
+      return res;
     }
 
     // First attempt to let any custom resolution logic provide a translation for the given node.