When the network client tests in this repo were copied over to the core
repo, some alterations were made. This commit copies them back to this
repo so that the two test suites are easier to compare to each other.
Changes include:
* Extracting `testsFor*` functions (functions that bundle similar tests
together) into separate files
* Reordering the tests defined in
`testsForRpcMethodsThatCheckForBlockHashInResponse`
* Reordering the set of RPC methods listed in `shared-tests.js`
* Reordering the type definitions defined in `shared-tests.js` to be
closer to the functions that use them
* Updating the tests defined in `testsForRpcMethodSupportingBlockParam`
so that when they make requests they pass params, even if it's just an
empty array
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