feat(providers): Log methods for PendingTransaction

[wolflo]

Motivation

I frequently want to print the transaction hash of a pending transaction before it is mined. Currently, this is pretty verbose, because you need a let binding for the transaction:

let tx = token.transfer(recipient, amt);
let pending = tx.send().await?;
println!("Tx hash: {:?}", *pending);
let mined = pending.await?;

Solution

Add two convenience methods on the PendingTransaction<_> type, log() and log_msg().

let mined = token.transfer(recipient, amt).send().await?.log_msg("Tx hash").await?;

Another approach that isn't just for printing might be to add a method to PendingTransaction<_> that returns (TxHash, Self), which would turn the above into:

let (hash, fut) = token.transfer(recipient, amt).send().await?.hash();
println!("Tx hash: {:?}", hash);
let mined = fut.await?;

PR Checklist

• Added Tests
• Added Documentation
• Updated the changelog

[mattsse]

I can see how this is useful,

alternatively we could make this akin to the std::iter::inscpect function:

pub fn inspect<F>(self, f: F) -> Self where F: FnMut(Self) {
   f(&self);
   self
}

so you can simply to

let mined = token.transfer(recipient, amt).send().await?.inspect(|tx| println!(".... {}", *tx)).await?;

[wolflo]

I like that too. I probably like the current version the least, because it's obviously use-case specific. Though maybe we want to keep log() and/or log_msg() in conjunction with a more useful version just for the succinctness.