[MLIR][NFC] Move presburger functionality from FlatAffineConstraints to IntegerPolyhedron

This patch moves all presburger functionality from FlatAffineConstraints to
IntegerPolyhedron. This patch is purely mechanical, it only moves and renames
functionality and tests.

This patch is part of a series of patches to move presburger functionality to
Presburger/ directory.

Reviewed By: bondhugula

Differential Revision: https://reviews.llvm.org/D116681