ARC-0034: Program Interfaces

[pa-long]

As of November 1st of 2023, an import instruction must always explicit a specific program id.

This implies that for most usecases manipulating implementations of a standard,
as many instances of the program must be deployed as the amount of standard implementations.

This is the case for instance for applications manipulating ARC-0020/ARC-0721 tokens exchange for example : escrows, auctions, pools.

Interfaces seem to be the most obvious solution to this problem,
extending widely composability on Aleo.

Discussions about ARC-0721, focusing on composability on aleo.

PR#44