Reenable Crossgen Tests

[v-wuzhai]

Summary

The current crossgen tests in the dotnet/sdk repository use the [Fact(Skip = "This coverage needs to be in core-sdk, which is where crossgen is applied")] attribute. This indicates that the coverage for these tests should be in the core-sdk repository, where crossgen is applied.

Specifically, the following two tests are skipped:

1. CLI_SDK_assemblies_must_be_crossgened
2. Shared_Fx_assemblies_must_be_crossgened

The reason for skipping these tests is that the crossgen process (precompiling assemblies to improve startup performance) is handled in the core-sdk repository. Therefore, tests related to crossgen should ideally be located in core-sdk. However, to improve traceability and provide context, we propose replacing the Skip attribute with a link to this PR. This change will help developers understand the reason for skipping these tests.

Expectation

We expect these two tests to be reenabled and properly executed within the appropriate context.