Extend BlockExt and LibFuncHelper and consolidate it across all the codebase

[edg-l]

The BlockExt and LibFuncHelper are on the right track to simplify code. We need to apply the existing abstractions across the whole source code, and some extensions could help as well.

One noticeable source of repetition in Starknet libfuncs is the handling of return values: filling payload_ok and payload_err takes 70loc per function. This could be extracted to a helper function.

Other sources of verbosity include arithmetic comparisons and function calls (including the lookup for the pointer, the getelementptr call and then afterwards the call itself). All of that would be more brief with helpers.