Implements Read on HexIterator

[RCasatta]

This would allow deserializing objects without allocating the intermediate byte vector like:

let tx = Transaction::consensus_decode(HexIterator::new("....").unwrap()).unwrap()

Especially useful for libraries like rust_bitcoincore_rpc in places like this https://github.com/rust-bitcoin/rust-bitcoincore-rpc/blob/54a427f2e45b0b8712d44a6995f6a03ad5f961f8/client/src/client.rs#L322-L326

CI is failing on my repo I think for an unrelated reason I am not fully grasping at the moment, @JeremyRubin could you have a look?

[apoelstra]

concept ACK. It's been a month, maybe worth just kicking the PR and see if CI is fixed?

[RCasatta]

I re-kicked (by re-pushing on a different branch, I havent't permission to re-kick here) https://github.com/RCasatta/bitcoin_hashes/actions/runs/1602919828 but it didn't work.

Now I noticed we have the same issue also in master https://github.com/rust-bitcoin/bitcoin_hashes/actions/runs/1602516688

[JeremyRubin]

weird, not sure what would have broken them.

I spent some time last month looking at this, but couldn't figure it out either.

[apoelstra]

I think it was fixed in #140

[RCasatta]

Rebased, thanks for the fix @JeremyRubin

[apoelstra]

ACK 60f51d9

Nice PR!

[stevenroose]

This looks super cool! :D