increase the number of partition test cases for test_partitioning_unstructured.py

Add the following cases to the partitioning tests in test_partitioning_unstructured.py. This results in many failing tests. This should be fixed or at least understood.

def case_two_parts(self, idomain_top) -> xu.UgridDataArray:
    two_parts = zeros_like(idomain_top)
    two_parts.values[74:] = 1
    return two_parts

def case_two_parts2(self, idomain_top) -> xu.UgridDataArray:
    two_parts = zeros_like(idomain_top)
    two_parts.values[47:] = 1
    return two_parts

def case_two_parts3(self, idomain_top) -> xu.UgridDataArray:
    two_parts = zeros_like(idomain_top)
    two_parts.values[147:] = 1
    return two_parts

def case_two_parts4(self, idomain_top) -> xu.UgridDataArray:
    two_parts = zeros_like(idomain_top)
    two_parts.values[187:] = 1
    return two_parts

def case_two_parts_inverse(self, idomain_top) -> xu.UgridDataArray:
    two_parts_inverse = zeros_like(idomain_top)
    two_parts_inverse.values[:74] = 1
    return two_parts_inverse

def case_two_parts_inverse2(self, idomain_top) -> xu.UgridDataArray:
    two_parts_inverse = zeros_like(idomain_top)
    two_parts_inverse.values[:47] = 1
    return two_parts_inverse

def case_two_parts_inverse3(self, idomain_top) -> xu.UgridDataArray:
    two_parts_inverse = zeros_like(idomain_top)
    two_parts_inverse.values[:147] = 1
    return two_parts_inverse

def case_two_parts_inverse4(self, idomain_top) -> xu.UgridDataArray:
    two_parts_inverse = zeros_like(idomain_top)
    two_parts_inverse.values[:187] = 1
    return two_parts_inverse

Start in test_partitioning_unstructured.py and add the eight specified partition cases to the existing partitioning test setup. Run the partitioning tests, then investigate the resulting failures; done means the added cases are covered and each failure is either fixed or clearly understood.