Spec cache system based on test decorators

[leolara]

Introduces a system to cache spec functions in tests

• Each test select which functions need to be cached for that test.
• The cache is shared between the tests that cache the same function.

This system is used in this PR to speed-up some PeerDAS tests, in my laptop in single-thread it reduces the total time in around 66%.

The new cache system is less than 240 lines of code, 1800+ plus lines are tests testing the system.

Note: currently the cache is not shared between parallel processes.

[jtraglia]

There's little benefit to this if it doesn't help multi-threaded test execution as well. The goal of this should be to noticeably reduce the CI's fulu tests step, which currently takes ~30 minutes.

[leolara]

There's little benefit to this if it doesn't help multi-threaded test execution as well. The goal of this should be to noticeably reduce the CI's fulu tests step, which currently takes ~30 minutes.

1. This is a new feature.

The previously accepted solution #4391 (https://github.com/ethereum/consensus-specs/pull/4391/files#diff-394c9e5d60550c94a80937fe82a9c448d67126e983797fc979c611c9c5628d48R160-R162)
did not have the feature of being multiprocess.

Also, proposed solution of using @functools.cache directly in specs also would not have worked in multi-process.

2. Multi-process cache can be added to this system. Not something really specially complicated, normal software engineering. However, it would be better to add it IMO in another PR, otherwise much more code to review at once.

Anyway, I can add it to this PR or in another PR.