[FEATURE] Copa+ congestion control algorithm

[umbrageodotus]

Pre-flight checklist

• I have searched existing issues/PRs and this has not been requested before.
• I have read the Contributing Guidelines.

Request type

• New patch / patchset inclusion
• Kernel config change (enable/disable option)
• New kernel variant
• Scheduler tuning / addition
• Compiler / LTO / PGO optimization
• Security hardening
• Driver or hardware enablement
• Other

Summary

Add the Copa+ congestion control algorithm as an option.

Motivation / use case

Copa+ would theoretically lower latency significantly (don't quote me on this though).

Patch / upstream reference (if available)

I'll make one if needed, or prove the paid Copa+ paper in order to permit an implementation.
Copa+ is a significant improvement to Copa consistency-wise, warranting the purchase of the paper (I'll do so if needed).

Testing / benchmarks

No response

Additional context

BBR has extreme bufferbloat issues, with Copa+ being surprisingly more stable (including studies displaying BBRv3's 0.95x of added latency, and BBRv1 is filled with such papers).