fix(compiler-cli): resolve type of exported *ngIf variable. (#33016)

Currently, method `getVarDeclarations()` does not try to resolve the type of
exported variable from *ngIf directive. It always returns `any` type.
By resolving the real type of exported variable, it is now possible to use this
type information in language service and provide completions, go to definition
and quick info functionality in expressions that use exported variable.
Also language service will provide more accurate diagnostic errors during
development.

PR Close #33016

packages/language-service/test/completions_spec.ts

@@ -55,6 +55,20 @@ describe('completions', () => {
     expectContains(fileName, 'name', 'name', 'street');
   });
 
+  it('should be able to get completions for exported *ngIf variable', () => {
+    const fileName = mockHost.addCode(`
+      interface Person {
+        name: string,
+        street: string
+      }
+
+      @Component({template: '<div *ngIf="promised_person | async as person">{{person.~{name}name}}</div'})
+      export class MyComponent {
+        promised_person: Promise<Person>
+      }`);
+    expectContains(fileName, 'name', 'name', 'street');
+  });
+
   it('should be able to infer the type of a ngForOf with an async pipe', () => {
     const fileName = mockHost.addCode(`
       interface Person {