chore: asRef for Log

[mattsse]

adds AsRef<Self> for Log

this is useful for because we have layered logs types (rpc::Log) and we'd like to have impl TxReveipt where T: AsRef<Log>

currently we use Borrow but this is semantically incorrect:

Borrow also requires that Hash, Eq and Ord for a borrowed value are equivalent to those of the owned value. For this reason, if you want to borrow only a single field of a struct you can implement AsRef, but not Borrow.
https://doc.rust-lang.org/std/convert/trait.AsRef.html