Add helper classes to declarative builders to help write end-to-end custom ops.

This CL adds the same helper classes that exist in the AST form of EDSCs to support a basic indexing notation and emit the proper load and store operations and capture MemRefViews as function arguments.

This CL also adds a wrapper class LoopNestBuilder to allow generic rank-agnostic loops over indices.

PiperOrigin-RevId: 237113755