Tests time-out instead of failing when exceptions thrown during layout pass

[Arlodotexe]

Describe the bug

Background

This was found while investigating Fix: DockPanel measure fix #618

Problem

If an exception is thrown during a XAML measure pass, the tests stall out and do not report the answer.

This seems to happen whether using the [UIThreadTestMethod] attribute from our TestGen tooling or when using [TestMethod], EnqueueAsync, LoadTestContentAsync and UnloadTestContentAsync piecemeal. The effect is the same.

Solution

This needs investigation and fixing. It's not helpful to simply time out when a control throws during a layout or measure pass, and it can become an active problem if unexpected errors aren't being bubbled up to CI.

Steps to reproduce

This can be reproduced by throwing an exception during the `Measure` or `Arrange` pass while running in a unit test. 

This can either be set up manually for a long-term repro, or it can be temporarily reintroduced by reverting https://github.com/CommunityToolkit/Windows/pull/618 and running.

Expected behavior

Tests should catch exceptions thrown during XAML layout and bubble them up instead of timing out.

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

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