[MLIR][Presburger] Make constructors from PresburgerSpace explicit

This patch makes constructors of IntegerRelation, IntegerPolyhedron,
PresburgerRelation, PresburgerSet from PresburgerSpace explicit. This
prevents bugs like:

```
void fun(IntegerRelation a, IntegerRelation b) {
  IntegerPolyhedron c = a.intersect(b);
}
```

Here, `a.intersect(b)` will return `IntegerRelation`, which will be implicitly
converted to `PresburgerSpace` and will use the `PresburgerSpace` constructor
for IntegerPolyhedron. Leading to loss of any constraints in the intersection
of `a` and `b`. After this patch, this will give a compile error.

Reviewed By: arjunp

Differential Revision: https://reviews.llvm.org/D122972