ci/test: speed up tests

[DaniPopes]

We use proptest and keccak256 a lot, so make them way faster for a very small, insignificant cost to compile time, which is cached anyway in CI.

Some slow tests on my machine and CI

• SealedBlockTests::proptest: 20s to 2s, CI 60s, to 3.2s
• timestamped_forks: 12.5s to 1.5s, CI 42.5s, to 4.7s
• fuzz_state_root_incremental: 11.1s to 2.15s, CI 25s, to 4.2s
• prune_receipts_by_logs: 3.5s to 0.5s

There are 2 tests that are hard coded to sleep 60s which is not ideal (long_read_transaction_safety_disabled), added in #6181 by @shekhirin. I don't know enough about that part of the code base to reduce their running time. #6994

stage_checkpoint_pruned and execute_intermediate_commit are flaky, the first run it times out, then runs fine.

Remaining slow tests are quite a few networking tests that also look hard coded to 5 / 10 seconds, like txn_manager_read_transactions_duration_unbounded, test_backoff_on_no_response, cc @emhane @mattsse if there's anything we can do to make them faster, or if there's even a point in doing so.

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I've removed partitions for integration tests since the total running time is <30s with a 5m compile time, there is no point in splitting them.

[mattsse]

lgtm!

can take a look at the net tests separately