CI: Add Mooncake plugin to CI

[Alexey-Rivkin]

What?

Add Mooncake Transfer Engine compilation and testing to NIXL CI pipeline.

Why?

Enable the plugin coverage in CI.

How?

1. Install Mooncake from source in .gitlab/build.sh before NIXL compilation.
2. Execute mooncake_backend_test in .gitlab/test_cpp.sh alongside other backend tests

[github-actions]

👋 Hi Alexey-Rivkin! Thank you for contributing to ai-dynamo/nixl.

Your PR reviewers will review your contribution then trigger the CI to test your changes.

🚀

[Alexey-Rivkin]

/build

[Alexey-Rivkin]

/build

[Alexey-Rivkin]

Issues

Compilation Warnings

Mooncake build fails due to warnings compiling the yalantinglibs dependency. Need to decide whether to suppress these warnings.

Plugin Unload Failure

Test C++ fails to unload the Mooncake plugin after test execution:

Loaded plugins after unload:
 - Mooncake
TEST FAILED: Dynamic Plugins are still loaded

[ovidiusm]

Adding @iyastreb who might be able to help

[iyastreb]

I use the same commands to build Mooncake in my Dockerfile
/labhome/iyastrebov/ws/bench/Dockerfile
I didn't experience any build issues, and Mooncake plugin was working fine
Maybe other dependencies or base image matters?