[Popup] Properly handle Android Back Button pressed

[TheCodeTraveler]

Description of Change

This PR updates protected override bool PopupPage.OnBackButtonPressed() to ensure we properly close the Popup using CloseAsync() when the Android Back Button is tapped by the user.

This ensures that the Task returned by ShowPopupAsync() completes when the Android Back Button is tapped.

Linked Issues

Fixes #2717
Fixes #2700

This fixes the Issue highlighted by @crwsolutions in their comment here: #2703 (comment).

Note: This does not close resolve the issue #2703. We currently unable to reproduce that Issue and are awaiting a sample reproduction to help us solve that Issue.

PR Checklist

• Has a linked Issue, and the Issue has been approved(bug) or Championed (feature/proposal)
• Has tests (if omitted, state reason in description)
• Has samples (if omitted, state reason in description)
• Rebased on top of main at time of PR
• Changes adhere to coding standard
• Documentation created or updated: https://github.com/MicrosoftDocs/CommunityToolkit/pulls

Additional information

SafeFireAndForget
Because protected override bool OnBackButtonPressed() does not return a Task, we are unable to use the await keyword. Since PopupPage.Close returns a Task, we use .SafeFireAndForget() to ensure we follow best practices and await its Task under the hood.

PopupResult
For the PopupResult, I am setting WasDismissedByTappingOutsideOfPopup to true for two reasons:

1. By tapping the Android Back button, the user did tap outside of the popup to close it
2. WasDismissedByTappingOutsideOfPopup = false requires PopupResult<T>.Result to be a value provided by the developer when programmatically closing the popup

[Copilot]

Pull Request Overview

This PR ensures that tapping the Android Back button properly closes the popup by calling CloseAsync() and uses SafeFireAndForget(), so the ShowPopupAsync() task completes as expected.

• Removed the unused Shell.SetPresentationMode block in the constructor.
• Added CommunityToolkit.Maui.Extensions for SafeFireAndForget.
• Updated OnBackButtonPressed to always call CloseAsync(...) and return true instead of delegating to base.

Comments suppressed due to low confidence (1)

src/CommunityToolkit.Maui/Views/Popup/PopupPage.shared.cs:113

• Consider adding unit or integration tests for OnBackButtonPressed to verify that CloseAsync is invoked and that ShowPopupAsync() completes when the Android Back button is pressed.

CloseAsync(new PopupResult(true), CancellationToken.None).SafeFireAndForget();