feat(AztecMacro): Function types and visibility

[spalladino]

Update the aztec macros so that we have:

• #[aztec(private)]: Private constrained functions
• #[aztec(public)]: Public constrained functions
• #[aztec(internal)]: Functions only callable via an aztec function call from the same contract (used with either of the two above)
• #[aztec(query)]: Unconstrained query function (requires unconstrained)
• unconstrained (no attribute): Unconstrained helper function that is inlined
• no attribute: Constrained helper function that is inlined

Before implementing this, we still need agreement on the name aztec(query).

Full discussion in this forum thread.

[nventuro]

I for one like query. It's distinct from other ethereum terms (e.g. it's not 'view'), so there'll be no confusion, and it nicely conveys the purpose.

We've also been toying with the idea of a fouth category, tentatively called 'provable', which would be functions whose execution you could easily prove off-chain (e.g. you'd submit a proof for NFT.owner_of(token_id) at some block number).