Optimize the `json_infra` tests

[SamWilsn]

The tests/json_infra folder contains two types of tests (at least at the time of writing): unit tests for EELS, and tests that execute the JSON fixtures created by EEST. For the purposes of this issue, we're going to ignore our unit tests and focus on the JSON fixtures.

The intent of the json_infra tests is to ensure that EELS is capable of executing the filled JSON fixtures, and not verifying that we correctly implement the Ethereum specification. The py3 and pypy3 workflows are responsible for correctness.

With that in mind, there's absolutely no reason for json_infra to take several hours to run.

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My plan (and feel free to come up with a completely different approach), is to use https://github.com/SamWilsn/minimize-tests to generate a minimum set of tests that cover everything, and adding --cov-fail-under=MIN to force us to regenerate the set when necessary.

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Another thought: #1666 (comment)

[DeborahOlaboye]

Hi @SamWilsn , I would like to work on this issue, can I proceed?

[SamWilsn]

Feel free to take a stab at it, but be warned, it may not be for the feint of heart.