Remove exception swallowing and update tests to exhibit expected behaviour

[bijington]

Description of Change

This doesn't technically fix any bugs but it does fix some inconsistencies in our unit tests. You may notice there are some Console.Writeline statements in this PR. What I have observed on occasion is that Closing is logged but Closed is not which makes me wonder if it is close to potentially reproducing #2703

Linked Issues

• Fixes #

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

[Copilot]

Pull Request Overview

This PR removes the old AddPopup helper to avoid swallowed exceptions and modernizes the unit tests to use short- and long-lived popup classes that correctly close themselves. Key changes include:

• Deleted the legacy internal AddPopup method from PopupService.shared.cs.
• Replaced all uses of MockSelfClosingPopup/MockPageViewModel in tests with ShortLivedSelfClosingPopup/ShortLivedMockPageViewModel (and related long-lived variants).
• Introduced new test popup types with configurable durations, added GC calls in open/close handlers, and updated the mock dispatcher to block for delays.

Reviewed Changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 3 comments.

File	Description
src/CommunityToolkit.Maui/Services/PopupService.shared.cs	Removed deprecated internal AddPopup method.
src/CommunityToolkit.Maui.UnitTests/Mocks/MockDispatcher.cs	Changed DispatchDelayed to use Thread.Sleep and return true.
src/CommunityToolkit.Maui.UnitTests/Layouts/StateContainerTests.cs	Switched to Assert.ThrowsAnyAsync for animation timeout tests.
src/CommunityToolkit.Maui.UnitTests/BaseHandlerTest.cs	Updated service registrations for the new popup/view-model types.