[UWP Renderer] Allow nested fallbacks

[anna-dingler]

Related Issue

Fixes #8324

Description

1. Added a try/catch block so that we can make the recursive call to RenderFallback if we catch E_PERFORM_FALLBACK

2. Call RenderFallback if no fallbackRenderer is found

3. If the last fallback element within nested fallback does not render, ancestorHasFallback will be true. This caused us to throw E_PERFORM_CALLBACK which is caught by the initial element. If this element did not have a fallback, it will be dropped.

   Ex: Container (does not have fallback) -> ChildElement -> Fallback1 -> Fallback2 -> Fallback3
   ChildElement, Fallback1, and Fallback2 all failed. When Fallback3 fails, it will try to get the fallback mechanism of it's ancestor (Fallback2) by throwing E_PERFORM_FALLBACK. However, this error will land on the Container since all of the other elements failed. Without a fallback mechanism, the Container will be dropped.

   To fix this issue, I added a try/catch block for when we call RenderFallback on a child element. In the catch, we can verify that the parent element actually has a fallback mechanism before throwing the error.

Sample Card

https://github.com/microsoft/AdaptiveCards/blob/main/samples/v1.2/Tests/ContainerDoubleFallback.json
https://github.com/microsoft/AdaptiveCards/blob/main/samples/v1.2/Tests/DeepFallback.json

How Verified

Verified manually on the AdaptiveCards Visualizer.

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