Reintroduce operators for testing framework

type:internal

For LIGO developers

This MR reintroduces operators. Two things are taken into account here:

• Performance: having the possibility of directly evaluating constants instead of going through the Michelson interpreter performs much better.
• Compatibility: containers (list, maps, etc.) and test types (such as typed_address or mutation) are in some cases not compatible, as container functions can be written directly in terms of Michelson, and executed using the Michelson interpreter; e.g. List.size will fail to manipulate a mutation list for example.

Changelog details: