Possible memory leak when reloading images in MarkdownTextBlock

[Arlodotexe]

Describe the bug

Found by Copilot in #771

When using IImageProvider, the _image instance is replaced with a new Image object from the provider. This means the Loaded event handler attached in Init() is lost, since it was attached to the original _image instance. However, since this code is already executing within the LoadImage handler and _loaded is set to true immediately after, this might work correctly. Consider whether the event handler should be detached from the old image or if there's a risk of memory leaks from the orphaned handler on the original image object.

Steps to reproduce

Unknown, need investigation.

Expected behavior

No memory leaks when images are changed.

Screenshots

No response

Code Platform

• UWP
• WinAppSDK / WinUI 3
• Web Assembly (WASM)
• Android
• iOS
• MacOS
• Linux / GTK

Windows Build Number

• Windows 10 1809 (Build 17763)
• Windows 10 1903 (Build 18362)
• Windows 10 1909 (Build 18363)
• Windows 10 2004 (Build 19041)
• Windows 10 20H2 (Build 19042)
• Windows 10 21H1 (Build 19043)
• Windows 11 21H2 (Build 22000)
• Other (specify)

Other Windows Build number

No response

App minimum and target SDK version

• Windows 10, version 1809 (Build 17763)
• Windows 10, version 1903 (Build 18362)
• Windows 10, version 1909 (Build 18363)
• Windows 10, version 2004 (Build 19041)
• Other (specify)

Other SDK version

No response

Visual Studio Version

No response

Visual Studio Build Number

No response

Device form factor

No response

Additional context

No response

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