[Accessibility] Screen reader does not announce InfoBar when toggled in Navigated event handler

### Describe the bug

There is an issue with the narrator announcement of an InfoBar when opened or closed in a Navigated event.

Narrator announcement work correctly when opened or closed on its own.

However, when navigating which triggers the InfoBar to be IsOpen = true, there is no screen reader announcement. NarratorBuddy shows it is being announced, but it cannot be heard. It seems to be overtaken by the NavigationView's selected menu item announcement.

When navigating where it closes the InfoBar, no announcement is made at all saying it is dismissed.

Here is a min repro app: https://github.com/miksalmon/InfoBarNarratorIssue

### Steps to reproduce the bug

1. Navigate to Page 1
2. Notice the InfoBar does not get announced
3. Navigate to Page 2
4. Notice the InfoBar dismissed does not get announced

### Actual behavior

1. InfoBar does not get announced when IsOpen is set to true (in a Navigated event handler)
2. InfoBar dismissed does not get announced when IsOpen is set to true (in a Navigated event handler)

### Expected behavior

InfoBar should be announced when IsOpen is set to true.
InfoBar dismissed should be announced when IsOpen is set to false.

This behaviour can be seen using the checkbox in the min repro app. When not tied to a Navigated event, it works correctly.

### Screenshots

_No response_

### NuGet package version

None

### Windows version

_No response_

### Additional context

_No response_

Start with the linked InfoBarNarratorIssue min repro and reproduce the behavior with Narrator. Compare InfoBar changes made in the Navigated event handler with the checkbox-driven changes, focusing on InfoBar IsOpen, NavigationView selection announcements, and the Navigated entry point. Done means opening and dismissing the InfoBar both produce audible announcements during navigation.

Written by the indexing model from the issue text.