Tree-sync friendly lookup sync tests

[dapplion]

Issue Addressed

• Step 0 of the tree-sync roadmap Tree sync #7678

Current lookup sync tests are written in an explicit way that assume how the internals of lookup sync work. For example the test would do:

• Emit unknown block parent message
• Expect block request for X
• Respond with successful block request
• Expect block processing request for X
• Response with successful processing request
• etc..

This is unnecessarily verbose. And it will requires a complete re-write when something changes in the internals of lookup sync (has happened a few times, mostly for deneb and fulu).

What we really want to assert is:

• WHEN: we receive an unknown block parent message
• THEN: Lookup sync can sync that block
• ASSERT: Without penalizing peers, without unnecessary retries

Proposed Changes

Keep all existing tests and add new cases but written in the new style described above. The logic to serve and respond to request is in this function fn simulate https://github.com/dapplion/lighthouse/blob/2288a3aeb11164bb1960dc803f41696c984c69ff/beacon_node/network/src/sync/tests/lookups.rs#L301

• It controls peer behavior based on a CompleteStrategy where you can set for example "respond to BlocksByRoot requests with empty"
• It actually runs beacon processor messages running their clousures. Now sync tests actually import blocks, increasing the test coverage to the interaction of sync and the da_checker.
• To achieve the above the tests create real blocks with the test harness. To make the tests as fast as before, I disabled crypto with TestConfig

Along the way I found a couple bugs, which I documented on the diff.

Review guide

Look at lighthouse/beacon_node/network/src/sync/tests/lookups.rs directly (no diff).

Other changes are very minor and should not affect production paths

[dapplion]

Bug found on testing, lookups may be stuck given this sequence of events

[dapplion]

Minor bug, we need to remove the peer from the sync states (e.g. self.block_lookups) then inject the disconnect events. Otherwise we may send requests to peers that are already disconnected. I don't think there's risk of sync getting stuck if libp2p rejects sending messages to disconnected peers, but deserves a fix anyway.

[mergify]

This pull request has merge conflicts. Could you please resolve them @dapplion? 🙏