SmartContracts: Pass the calls to Interpreter.execute/3 & create corresponding message

[bchamagne]

Description

Create a GetContractCalls message. Then refactor the Interpreter.execute/3 to have the calls as a parameter instead of doing some I/O from within the contract execution.

The Contract.get_calls() is actually not really necessary anymore and we could tell the users there is a calls global variable available.

I entirely removed the get_calls function from Legacy interpreter since it did not work at all anyway.
I also only added it for the action blocks since there are no use case to handle it in condition block.

This PR is based on the branch #963. We need to rebase it after the merge

Fixes #926

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Unit tests ✔️
Manual test (faucet smart contract): ✔️

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules