Only mark block lookups as pending if block is importing from gossip (#8112)

- PR https://github.com/sigp/lighthouse/pull/8045 introduced a regression of how lookup sync interacts with the da_checker.

Now in unstable block import from the HTTP API also insert the block in the da_checker while the block is being execution verified. If lookup sync finds the block in the da_checker in `NotValidated` state it expects a `GossipBlockProcessResult` message sometime later. That message is only sent after block import in gossip.

I confirmed in our node's logs for 4/4 cases of stuck lookups are caused by this sequence of events:
- Receive block through API, insert into da_checker in fn process_block in put_pre_execution_block
- Create lookup and leave in AwaitingDownload(block in processing cache) state
- Block from HTTP API finishes importing
- Lookup is left stuck

Closes https://github.com/sigp/lighthouse/issues/8104


  - https://github.com/sigp/lighthouse/pull/8110 was my initial solution attempt but we can't send the `GossipBlockProcessResult` event from the `http_api` crate without adding new channels, which seems messy.

For a given node it's rare that a lookup is created at the same time that a block is being published. This PR solves https://github.com/sigp/lighthouse/issues/8104 by allowing lookup sync to import the block twice in that case.


Co-Authored-By: dapplion <35266934+dapplion@users.noreply.github.com>

beacon_node/beacon_chain/src/beacon_block_streamer.rs

@@ -404,7 +404,7 @@ impl<T: BeaconChainTypes> BeaconBlockStreamer<T> {
         if self.check_caches == CheckCaches::Yes {
             match self.beacon_chain.get_block_process_status(&root) {
                 BlockProcessStatus::Unknown => None,
-                BlockProcessStatus::NotValidated(block)
+                BlockProcessStatus::NotValidated(block, _)
                 | BlockProcessStatus::ExecutionValidated(block) => {
                     metrics::inc_counter(&metrics::BEACON_REQRESP_PRE_IMPORT_CACHE_HITS);
                     Some(block)