Event-based block lookup tests (#5534)

* WIP

* Initial working version of new sync tests.

* Remove sync traits and fix lints.

* Reduce internal method visibility and make test method instead. Remove extra beacon chain harness instance created in tests.

* Improve `SyncTester` api.

* Fix lint.

* Test example

* Lookup tests using rig

* Tests should interface with events only

* lint

* Skip deneb test pre-deneb

* Add more assertions

* Remove logging changes

* Address @jimmygchen comments

* Merge branch 'unstable' of https://github.com/sigp/lighthouse into bn-p2p-tests

* remove unused assertions

* fix lint

beacon_node/beacon_chain/src/test_utils.rs

@@ -2498,6 +2498,7 @@ pub fn build_log(level: slog::Level, enabled: bool) -> Logger {
 
 pub enum NumBlobs {
     Random,
+    Number(usize),
     None,
 }
 
@@ -2518,6 +2519,7 @@ pub fn generate_rand_block_and_blobs<E: EthSpec>(
             let payload: &mut FullPayloadDeneb<E> = &mut message.body.execution_payload;
             let num_blobs = match num_blobs {
                 NumBlobs::Random => rng.gen_range(1..=E::max_blobs_per_block()),
+                NumBlobs::Number(n) => n,
                 NumBlobs::None => 0,
             };
             let (bundle, transactions) =
@@ -2537,6 +2539,7 @@ pub fn generate_rand_block_and_blobs<E: EthSpec>(
             let payload: &mut FullPayloadElectra<E> = &mut message.body.execution_payload;
             let num_blobs = match num_blobs {
                 NumBlobs::Random => rng.gen_range(1..=E::max_blobs_per_block()),
+                NumBlobs::Number(n) => n,
                 NumBlobs::None => 0,
             };
             let (bundle, transactions) =