[Flang][OpenMP] Support iterator modifiers in map and motion clauses
Support iterated array elements and array sections in map and motion clauses for
target data, target enter data, target exit data, and target update constructs.
Preserve mapper resolution for iterated entries, including explicit mappers,
user-defined default mappers, declare mapper entries, and implicit default
mappers.
This PR stacked on top of #197047 and #197752.
This patch is part of the feature work for #188061.
Assisted with copilot.