[flang][OpenMP] Support lowering to MLIR for ordered clause

This supports the lowering parse-tree to MLIR for ordered clause in
worksharing-loop directive. Also add the test case for operation
conversion.

Part of this patch is from the fir-dev branch of
https://github.com/flang-compiler/f18-llvm-project

.

Co-authored-by: Sourabh Singh Tomar <SourabhSingh.Tomar@amd.com>

Reviewed By: kiranchandramohan, NimishMishra

Differential Revision: https://reviews.llvm.org/D125456