devel/libcircle: New port: API to distribute parallel workloads across MPI ranks

libcircle provides an API for distributing embarrassingly parallel
workloads across MPI ranks using a distributed work queue.

Applications register callbacks to create and process work items, while
the library handles load balancing, termination detection, and optional
global reductions. It is commonly used on large HPC filesystems to
traverse directory trees and perform file operations in parallel on
hundreds or thousands of processes.

https://github.com/hpc/libcircle

It is one of the dependencies for sysutils/mpifileutils.

PR: 291589
Sponsored by: UNIS Labs
Co-authored-by: Vladimir Druzenko <vvd@FreeBSD.org>