Related to #58194

Failing test cases include:

• ExpressionCompilerTests.AsyncRewriterIgnoreAccessibility
• ExpressionCompilerTests.Await
• ExpressionCompilerTests.AwaitInUnsafeContext
• DynamicTests.AwaitDynamic
• ResultPropertiesTests.Error

Sample run: https://dev.azure.com/dnceng/public/_build/results?buildId=1503687&view=ms.vss-test-web.build-test-results-tab&runId=42860136&resultId=207156&paneView=debug

The 2 causes I see are:

1. lambda/method group implicit type has changed some expectations.
2. Some IAsyncEnumerable changes with lambdas. Lambda symbols assume their DeclaringCompilation is not null.

FYI @cston @jcouv