Run tests under CoreCLR

[grendello]

This PR actually enables building of the CoreCLR host added to
main in #9572

The goal is to fix all the failing tests, possibly add new ones.

[grendello]

/azp run

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[grendello]

/azp run

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[grendello]

/azp run

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[grendello]

/azp run

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[grendello]

/azp run

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[grendello]

/azp run

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[grendello]

/azp run

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[pjcollins]

Given the timeframe for 'official' support I think we may be better served by incrementally adding tests for additional runtime configurations? For instance, Peppers has a WIP Mono.Android tests flavor addition here #9916 which will bring in some CoreCLR coverage.

In addition to that, perhaps we could just parameterize one or more of the Build/Packaging and Deploy/Debug tests to run against CoreCLR for now, rather than duplicating all of our test stages?

As we get closer to 'official' support we'll need to reevaluate and determine whether we want all PR builds to run all tests against all runtime flavors (similar to the current approach in this PR). Some alternatives to this approach that may be worth considering would be:

• Adding duplicate test stages for new runtime flavors to the nightly build
• Creating additional separate pipeline(s) that can be triggered automatically or manually based on certain code path changes or when we otherwise determine we want additioinal runtime flavor coverage