Consolidation with CDI-PIO (develop)

Generally, this is !11 (merged) rebased onto the develop branch.

This is the first develop-based version accepted by the Buildbot of ICON: https://buildbot.dkrz.de/grid?branch=m300488/cdi-pio-2-integration

tests/deco2d_model.c

@@ -277,13 +277,6 @@ modelRun(struct model_config setup, MPI_Comm comm)
                 {
 #if USE_MPI
                   xt_redist_s_exchange1(varDesc[varIdx].redist4gather, varslice, var);
-                  size_t layerSize = (size_t) (chunk[0] * chunk[1]);
-                  size_t nblk = (layerSize + nproma - 1) / nproma - 1;
-                  for (size_t k = 0; k < varLevs; ++k)
-                    {
-                      blk_displ[k] = (int) (k * (nblk + 1) * nproma);
-                      blk_lens[k] = (int) layerSize;
-                    }
 #else
                   size_t layerSize = (size_t) (chunk[0] * chunk[1]);
                   size_t nblk = (layerSize + nproma - 1) / nproma - 1;
@@ -305,6 +298,13 @@ modelRun(struct model_config setup, MPI_Comm comm)
                 }
 
 #ifdef USE_MPI
+              size_t layerSize = (size_t) (chunk[0] * chunk[1]);
+              size_t nblk = (layerSize + nproma - 1) / nproma - 1;
+              for (size_t k = 0; k < varLevs; ++k)
+                {
+                  blk_displ[k] = (int) (k * (nblk + 1) * nproma);
+                  blk_lens[k] = (int) layerSize;
+                }
               streamWriteScatteredVarPart(streamID, varDesc[varIdx].id, varslice, (int) varLevs, blk_lens, blk_displ, nmiss,
                                           varDesc[varIdx].partDesc);
 #else