This patch makes the following changes to SparseTensorDimSliceAttr methods:
- Mark isDynamic constexpr.
- Add new helpers getStatic and getStaticString to avoid repetition.
- Moved the definitions for getStatic{Offset,Stride,Size} and isCompletelyDynamic out of the class declaration; because there's no benefit to inlining them.
- Changed parse to use kDynamic rather than literals.
- Changed verify to use the isDynamic helper.
Why call getStaticString when the v can be dynamic?