feat(core): Transaction::decode() sets the hash

[achillelamb]

Fixes: #1849

Motivation

As stated in issue #1849, when the function decode(rlp) is used to build a transaction from its rlp serialization (i.e. raw transaction) the field hash of the resulting Transaction is not set (set to default value, hash 0x0).

Solution

The hash field of the returned Transaction is calculated as the keccak256 of the rlp bytes.

The test for the correctness of this change can be run with

cargo test --package ethers-core types::transaction::response::tests::decode_tx_assert_hash

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[prestwich]

concept ack, running checks

[prestwich]

tests and build work, CI issues are unrelated. Gonna go ahead and merge