[MLIR][Presburger] Remove inheritence in MultiAffineFunction

This patch removes inheritence of MultiAffineFunction from IntegerPolyhedron
and instead makes IntegerPolyhedron as a member.

This patch removes virtualization in MultiAffineFunction and also removes
unnecessary functions inherited from IntegerPolyhedron.

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D123921