psblas3/test/comm/swapdata

swapdata communication test

This test was added after introducing different communication schemes in PSBLAS.

It focuses on direct halo exchange through the swapdata path:

• index list type: halo (psb_comm_halo_)
• exchange API: psi_swapdata
• phases: start, wait, and sync (depending on test section)

Communication patterns exercised:

• baseline point-to-point (isend/irecv)
• neighbor collective (ineighbor_alltoallv)
• persistent neighbor collective (persistent_ineighbor_alltoallv)

This test validates the low-level communication behavior in isolation, without the full SpMV overlap pipeline.