Write range sync tests in external event-driven form

[dapplion]

Issue Addressed

Re-write existing range sync tests into an event-driven format to accommodate the refactor introduced in

• Add individual by_range sync requests #6497

This format was introduced in

• Event-based block lookup tests #5534

and does not make assumptions about internal functions, it treats sync as a black box inputting actual events used in production.

Note: I've removed the generics used in range sync since now we don't unit test directly

[jimmygchen]

I don't really understand what this line does - do we need to assert for some condition after doing this?

[dapplion]

I respected the original test sequence as written in #2827, it covered a bug which this final line triggered a debug assertion

[jimmygchen]

Nice! Looks clean and easy to read 👍

[dapplion]

    sync::tests::range::state_update_while_purging
test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 86 filtered out; finished in 7.58s

──── STDERR:             network sync::tests::range::state_update_while_purging
thread 'sync::tests::range::state_update_while_purging' panicked at /home/runner/work/lighthouse/lighthouse/beacon_node/beacon_chain/src/test_utils.rs:904:14:
called `Result::unwrap()` on an `Err` value: ExecutionLayerMissing

This test is failing in CI after switching to async, but can't reproduce locally