fix(compiler): source span for microsyntax text att should be key span (#38766)

In a microsyntax expressions, some attributes are not bound after
desugaring. For example,
```html
<div *ngFor="let item of items">
</div>
```
gets desugared to
```html
<ng-template ngFor let-items [ngForOf]="items">
</ngtemplate>
```
In this case, `ngFor` should be a literal attribute with no RHS value.
Therefore, its source span should be just the `keySpan` and not the
source span of the original template node.
This allows language service to precisely pinpoint different spans in a
microsyntax to provide accurate information.

PR Close #38766

packages/language-service/ivy/test/hybrid_visitor_spec.ts

@@ -487,8 +487,9 @@ describe('findNodeAtPosition for microsyntax expression', () => {
     // <ng-template ngFor let-item [ngForOf]="items">
     expect(errors).toBe(null);
     const node = findNodeAtPosition(nodes, position);
-    // TODO: this is currently wrong because it should point to ngFor text
-    // attribute instead of ngForOf bound attribute
+    expect(isTemplateNode(node!)).toBeTrue();
+    expect(node).toBeInstanceOf(t.TextAttribute);
+    expect((node as t.TextAttribute).name).toBe('ngFor');
   });
 
   it('should locate not let keyword', () => {