fix: eip1559 validation incorrectly adds gas price field

[banteg]

What was wrong?

When passing a correct EIP-1559 transaction with:

{'maxFeePerGas': '0x174876e800', 'maxPriorityFeePerGas': '0x77359400', 'type': '0x2'}

validate_transaction_params appends gasPrice to it, which causes the subsequent check for mixed transaction type to fail.

{'maxFeePerGas': '0x174876e800', 'maxPriorityFeePerGas': '0x77359400', 'type': '0x2', 'gasPrice': '0x6977bbb6'}

How was it fixed?

Expanded the condition to skip adding gasPrice when maxPriorityFeePerGas key is present.

Todo:

• Add entry to the release notes

[fselmo]

I like this addition... so when we have a gas price strategy set but want to send an EIP-1559 transaction, we can still do so. I think I'd like to expand this to something like:

Suggested change

	and 'maxPriorityFeePerGas' not in transaction
	and all(_ not in transaction for _ in ('maxFeePerGas', 'maxPriorityFeePerGas'))

This way, if only maxFeePerGas is specified, we end up with a better message on why the exception was thrown. It won't be confusing that a gas price was added and conflicted, instead it will be that the maxPriorityFeePerGas needs to be explicit for an EIP-1559 transaction.

[fselmo]

I also am going to encourage adding a test to eth_module for this. If you'd like I can throw one in on top of this change. Let me know.

[fselmo]

I would add here that this was only when a gas price strategy is explicitly set

[fselmo]

This newsfragment also needs to be in .rst format. This is why the build failed.

[kclowes]

@fselmo LGTM once the error variants of the test are split out like we talked about! 🚢

[fselmo]

@banteg thanks for the PR. I went ahead and added the tests I mentioned and merged so we can get this out in the next release.