pygeos-tools: implement gatherField method to collect a field across all rank with correct ghostRank and localToGlobalMap

[alexbenedicto]

In pygeos-tools, when working with multiple ranks, no method is able yet to gather fields across all ranks wrt ghostRank and localToGlobalMap.

Currently, the closest method to perform this task is:

geosPythonPackages/pygeos-tools/src/geos/pygeos_tools/wrapper.py

Line 45 in 7bccab6

def get_wrapper_par( problem: pygeosx.Group, target_key: str, allgather=False, ghost_key: str = '' ) -> np.ndarray:

The issue is that the fields are concatenated in the order of the ranks and not by taking into account the localToGlobalMap.
The goal would be to use that localToGlobalMap in a new improved method.