Fix memory leak on snackbar

[pictos]

Description of Change

Use WeakReference for the Anchor property.

Linked Issues

• Fixes [BUG] A Snackbar that specifies an Anchor will continue to retain the Anchor inside the Snackbar even after it is dismissed. #3031

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 pull request fixes a memory leak in the Snackbar component by using a WeakReference to store the Anchor property, preventing the Snackbar from keeping strong references to UI elements that should be garbage collected.

Changes:

• Added a new WeakReferenceExtensions class with a GetTargetOrDefault extension method for convenient WeakReference handling
• Modified the Anchor property in Snackbar to use WeakReference for storage instead of directly storing the IView reference
• Minor formatting fix to a documentation comment

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/CommunityToolkit.Maui/Extensions/WeakReferenceExtensions.cs	New extension method to simplify retrieving WeakReference targets
src/CommunityToolkit.Maui/Alerts/Snackbar/Snackbar.shared.cs	Modified Anchor property to use WeakReference backing field; minor comment formatting correction

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.