- add comments to hashes shim
- remove .catch from callback condition
- derive SignerError from EthersError instead of ProviderError. This allows Providers and Signers to be separate, as Ledger does it, to isolate functionality. Some signer functions now raise both ProviderError and SignerError
- Update reverts to check for SignerError
- Update ERC-20 method comment
- async lock during nonce sequencing + gas estimation
- simplified cancelTransaction (still exported) such that the new transaction is populated using populateTransaction, so that all gas and fees are reset
- moved reverting contract function into its own testing helpers module, and refactored any tests to use it
- updated the test helper reverts to check EstimateGasErrors
- combine ensureNonceSequence into populateTransaction
1. rename helpers to testing and expose externally via `import pkg/ethers/testing`
2. Change detection of revert from `EthersError` to `JsonRpcProviderError`
3, Remove catch of `CatchableError` from revert detection as this would swallow errors. Update tests accordingly.