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

src/pio_interface.c

@@ -81,15 +81,6 @@ memcpyPackFunc(void *dataDesc, void *buf, int size, int *pos, void *context)
 
 /****************************************************/
 
-struct clientBufferSetup
-{
-  struct collSpec collectData;
-  struct clientBufSize *bufSizes;
-  size_t bufSizesCount;
-};
-
-/************************************************************************/
-
 static void
 modelWinFlushBuffer(size_t streamIdx)
 {