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_impl.h

@@ -96,7 +96,7 @@ void cdiPioFileWriteOrderedInit(void);
 void cdiPioFileWriteAtAllInit(void);
 
 /* pio_mpi_fw_at_reblock.c */
-void cdiPioFileWriteAtReblockInit(const struct cdiPioConf *conf);
+void cdiPioFileWriteAtReblockInit(void);
 
 /* common functionality for file split between collectors and writer(s) */
 void pioSendInitialize(void);