Revert "[MLIR] rewrite AffineStructures and Presburger tests to use the parser"

This reverts commit b0e8667b.

ASAN/UBSAN bot is broken with this trace:

[ RUN      ] FlatAffineConstraintsTest.FindSampleTest
llvm-project/mlir/include/mlir/Support/MathExtras.h:27:15: runtime error: signed integer overflow: 1229996100002 * 809999700000 cannot be represented in type 'long'
    #0 0x7f63ace960e4 in mlir::ceilDiv(long, long) llvm-project/mlir/include/mlir/Support/MathExtras.h:27:15
    #1 0x7f63ace8587e in ceil llvm-project/mlir/include/mlir/Analysis/Presburger/Fraction.h:57:42
    #2 0x7f63ace8587e in operator* llvm-project/llvm/include/llvm/ADT/STLExtras.h:347:42
    #3 0x7f63ace8587e in uninitialized_copy<llvm::mapped_iterator<mlir::Fraction *, long (*)(mlir::Fraction), long>, long *> include/c++/v1/__memory/uninitialized_algorithms.h:36:62
    #4 0x7f63ace8587e in uninitialized_copy<llvm::mapped_iterator<mlir::Fraction *, long (*)(mlir::Fraction), long>, long *> llvm-project/llvm/include/llvm/ADT/SmallVector.h:490:5
    #5 0x7f63ace8587e in append<llvm::mapped_iterator<mlir::Fraction *, long (*)(mlir::Fraction), long>, void> llvm-project/llvm/include/llvm/ADT/SmallVector.h:662:5
    #6 0x7f63ace8587e in SmallVector<llvm::mapped_iterator<mlir::Fraction *, long (*)(mlir::Fraction), long> > llvm-project/llvm/include/llvm/ADT/SmallVector.h:1204:11
    #7 0x7f63ace8587e in mlir::FlatAffineConstraints::findIntegerSample() const llvm-project/mlir/lib/Analysis/AffineStructures.cpp:1171:27
    #8 0x7f63ae95a84d in mlir::checkSample(bool, mlir::FlatAffineConstraints const&, mlir::TestFunction) llvm-project/mlir/unittests/Analysis/AffineStructuresTest.cpp:37:23
    #9 0x7f63ae957545 in mlir::FlatAffineConstraintsTest_FindSampleTest_Test::TestBody() llvm-project/mlir/unittests/Analysis/AffineStructuresTest.cpp:222:3