refactor: add client entity to smart contracts

[mversic]

Context

• introduce a host handle that smart contract writers use to interact with the host environment
• introduce context of the execution that every smart contract is given (in the future this should be header of the block that is currently executing)
• change all smart contract functions to receive (host, context)
• rename Validate trait to Execute

Closes #4898

Migration guide

• this is a breaking change for all smart contracts

Previous API:

#[iroha_trigger::main]
fn main(id: TriggerId, owner: AccountId, event: EventBox) {
    let EventBox::ExecuteTrigger(event) = event else {
        dbg_panic("Only work as by call trigger");
    };

    let rose_id = AssetId::new("rose#wonderland".parse().unwrap(), owner);
    let val: u32 = query_single(FindTriggerMetadata::new(id, "VAL".parse().unwrap()))
}

New API:

#[iroha_trigger::main]
fn main(host: Iroha, context: Context) {
    let EventBox::ExecuteTrigger(event) = context.event else {
        dbg_panic("Only work as by call trigger");
    };

    let rose_id = AssetId::new("rose#wonderland".parse().unwrap(), context.authority);
    let val: u32 = host
        .query_single(FindTriggerMetadata::new(context.id, "VAL".parse().unwrap()))
        .dbg_unwrap()
        .try_into_any()
        .dbg_unwrap();
}

[mversic]

the unfortunate difference from iroha client is that we take instruction by reference instead of value

[mversic]

IMO carries too much mental overhead for the end user. Can we simplify it?

[Erigara]

If they always used together we can combine them.

[Erigara]

I think since this is breaking change for smart-contracts, migration guide should be provided.

[Erigara]

If they always used together we can combine them.