Consolidate all the test utilities in rpc tests #4093
Description
In the test/rpc subfolder in the client tests, there is some duplication of test utilities with small adjustments that should be consolidated. This is mainly in the test/rpc/eth tests where you have duplication of things like produceBlockWith4844Tx in both blobBaseFee and getFeeHistory tests.
Where possible, we should deduplicate all thse tests and move them to test/rpc/helpers.ts (or else create a new subfolder with specific files for various helper types if helpers.ts is too unwieldy).
This could be a great job for Claude and somebody with a little patience.