fix(ivy): template inputs/outputs should not be bound in template scope (#30669)

The R3TargetBinder "binds" an Angular template AST, computing semantic
information regarding the template and making it accessible.

One of the binding passes previously had a bug, where for the following
template:

<div *ngIf="foo as foo"></div>

which desugars to:

<ng-template ngIf [ngIf]="foo" let-foo="ngIf">
  <div></div>
</ng-template>

would have the `[ngIf]` binding processed twice - in both the scope which
contains the `<ng-template>` and the scope inside the template. The bug
arises because during the latter, `foo` is a variable defined by `let-foo`,
and so the R3TargetBinder would incorrectly learn that `foo` inside `[ngIf]`
maps to that variable.

This commit fixes the bug by only processing inputs, outputs, and
templateAttrs from `Template`s in the outer scope.

PR Close #30669

packages/compiler/src/render3/view/t2_binder.ts

@@ -372,12 +372,8 @@ class TemplateBinder extends RecursiveAstVisitor implements Visitor {
 
   private ingest(template: Template|Node[]): void {
     if (template instanceof Template) {
-      // For <ng-template>s, process inputs, outputs, template attributes,
-      // variables, and child nodes.
-      // References were processed in the scope of the containing template.
-      template.inputs.forEach(this.visitNode);
-      template.outputs.forEach(this.visitNode);
-      template.templateAttrs.forEach(this.visitNode);
+      // For <ng-template>s, process only variables and child nodes. Inputs, outputs, templateAttrs,
+      // and references were all processed in the scope of the containing template.
       template.variables.forEach(this.visitNode);
       template.children.forEach(this.visitNode);