The control flow migration was incorrectly removing ng-template elements in scenarios where they were referenced by multiple *ngIf directives' else clauses and also used independently via ngTemplateOutlet.

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/angular/angular/blob/main/contributing-docs/commit-message-guidelines.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• angular.dev application / infrastructure changes
• Other... Please describe:

What is the current behavior?

Template:

<div *ngIf="1 == 1; else elseTemplate">
  <h1>TEST</h1>
</div>
<div *ngIf="1 == 1; else elseTemplate">
  <h1>TEST</h1>
</div>

<ng-container [ngTemplateOutlet]="elseTemplate"></ng-container>
<ng-template #elseTemplate>
  <h1>Test</h1>
  <div>Test</div>
</ng-template>

After:

@if (1==1) {
  <div>
    <h1>TEST</h1>
  </div>
} @else {
  <h1>Test</h1>
  <div>Test</div>
}

@if (1==1) {
  <div>
    <h1>TEST</h1>
  </div>
} @else {
  <h1>Test</h1>
  <div>Test</div>
}
<ng-container [ngTemplateOutlet]="elseTemplate"></ng-container>

What is the new behavior?

This change updates the template processing logic to correctly detect all usages of a template, including property-bound [ngTemplateOutlet]. The migration will now preserve the ng-template if it's still referenced after the *ngIf directives have been migrated.

Now:

@if (1 == 1) {
<div><h1>TEST</h1></div>
} @else {
<h1>Test</h1>
<div>Test</div>
} @if (1 == 1) {
<div><h1>TEST</h1></div>
} @else {
<h1>Test</h1>
<div>Test</div>
} <ng-container [ngTemplateOutlet]="elseTemplate"></ng-container>
<ng-template #elseTemplate>
  <h1>Test</h1>
  <div>Test</div>
</ng-template>

Does this PR introduce a breaking change?

• Yes
• No