[Polly] Refabricating IsOutermostParallel() from Integer Set Libarary(ISL) to take the C++ wrapper

Polly use algorithms from the Integer Set Library (isl), which is a library written in C and which is incompatible with the rest of the LLVM  as it is written in C++.

Changes made:
* Refabricating IsOutermostParallel() to take C++ bindings instead of reference-counting in C isl lib.
* Addition of manage_copy() to be used as reference for C objects instead of IsOutermostParallel()

Reviewed By: Meinersbur

Differential Revision: https://reviews.llvm.org/D97751