Expand the CI pipeline to include builds setting `UseExperimentalWinUI3` flag

[jonthysell]

Summary

PR #12674 added a build flag UseExperimentalWinUI3 to use experimental, internal builds of WinAppSDK for testing experimental APIs. We will want the CI pipeline to include that configuration in it's build/test matrix.

Motivation

In order to influence the design of future WinAppSDK APIs, we need to be able to build/test against pre-release versions of the WinAppSDK. To do that rigorously we need the CI pipelines to be able to run in that setup.

Basic Example

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Open Questions

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