This commit switches the current implementation of
'partitionCellsZoltan()', i.e., 'partitionCells("zoltan", ...)' into
using the MPI-aware ParallelNLDDPartitioningZoltan utility. In
doing so we make 'partitionCellsZoltan()' private since its
availability is not guaranteed. We also slightly reorder the
parameters and switch from passing a "Grid" into passing a
"GridView" as an argument to partitionCells(), and specialise this
function for the known grid views in OPM Flow.
We extract the Zoltan-related parameters out to an Entity-dependent
helper structure and move the complexity of forming this type to a
new helper function, BlackoilModelEbosNldd::partitionCells().
Invokes Zoltan library and requires MPI. Client code constructs an
abstract connectivity graph by defining connections/edges through
the 'registerConnection()' member function. May also impose a
restriction that certain cells/vertices be placed in the same
domain/block in the resulting partition. Client code must supply a
callback function that defines globally unique cell/vertex/object
IDs, across all MPI ranks, for each vertex in the connectivity
graph.
Member function 'partitionElement()' forms the resulting partition
vector, the size of which is the total number of objects visible to
the local rank-typically the number of cells owned by the rank, and
the number of overlap cells--i.e., the size of the local grid view.
