Gloas payload cache (#9209)

In Gloas, beacon blocks are imported into fork choice immediately - the payload envelope and data columns arrive
separately. KZG commitments moved from the column sidecar into the execution payload bid, so the existing
`DataAvailabilityChecker` (which assumes block and data are coupled) can't be used for Gloas.


  * Introduced `PendingPayloadCache` to keep track of payload and data columns per block root.
* Added gossip column verification
* Added support for Gloas data column reconstruction
* Payload envelope verification simplified: removed `MaybeAvailableEnvelope`, `ExecutedEnvelope`, `EnvelopeImportData`

Not yet implemented (tracked with TODOs):
- Proper lookup sync for Gloas columns arriving before blocks
- Partial column merging for Gloas
- Moving `load_gloas_payload_bid` disk reads off the async runtime
- Backfill/range sync for Gloas

Based on @eserilev's PR and work in progress. See also #9202 for verification.


Co-Authored-By: Eitan Seri-Levi <eserilev@ucsc.edu>

Co-Authored-By: Eitan Seri- Levi <eserilev@gmail.com>

Co-Authored-By: Daniel Knopik <daniel@dknopik.de>

Co-Authored-By: Daniel Knopik <107140945+dknopik@users.noreply.github.com>

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

Co-Authored-By: Jimmy Chen <jchen.tc@gmail.com>

beacon_node/beacon_chain/src/canonical_head.rs

@@ -988,6 +988,25 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
                 .start_slot(T::EthSpec::slots_per_epoch()),
         );
 
+        // Prune the Gloas pending-payload cache. Anything older than the data-availability
+        // boundary cannot still be in flight; finalised entries are also safe to drop.
+        if self.spec.gloas_fork_epoch.is_some() {
+            let finalized_epoch = new_view.finalized_checkpoint.epoch;
+            let current_epoch = new_snapshot
+                .beacon_state
+                .slot()
+                .epoch(T::EthSpec::slots_per_epoch());
+            if let Some(min_epochs_for_blobs) = self
+                .spec
+                .min_epoch_data_availability_boundary(current_epoch)
+            {
+                let cutoff_epoch = std::cmp::max(finalized_epoch + 1, min_epochs_for_blobs);
+                if let Err(e) = self.pending_payload_cache.do_maintenance(cutoff_epoch) {
+                    error!(error = ?e, "Failed to prune pending payload cache on finalization");
+                }
+            }
+        }
+
         if let Some(event_handler) = self.event_handler.as_ref()
             && event_handler.has_finalized_subscribers()
         {