Add blob_sidecar event to SSE (#4790)

* Add `blob_sidecar` event to SSE.

* Return 202 if a block is published but failed blob validation when validation level is `Gossip`.

* Move `BlobSidecar` event to `process_gossip_blob` and add test.

* Emit `BlobSidecar` event when blobs are received over rpc.

* Improve test assertions on `SseBlobSidecar`s.

* Add quotes to blob index serialization in `SseBlobSidecar`

Co-authored-by: realbigsean <seananderson33@GMAIL.com>

---------

Co-authored-by: realbigsean <seananderson33@GMAIL.com>

beacon_node/beacon_chain/src/blob_verification.rs

@@ -10,7 +10,7 @@ use crate::block_verification::cheap_state_advance_to_obtain_committees;
 use crate::data_availability_checker::AvailabilityCheckError;
 use crate::kzg_utils::{validate_blob, validate_blobs};
 use crate::{metrics, BeaconChainError};
-use kzg::Kzg;
+use kzg::{Kzg, KzgCommitment};
 use slog::{debug, warn};
 use ssz_derive::{Decode, Encode};
 use ssz_types::VariableList;
@@ -182,6 +182,12 @@ impl<T: BeaconChainTypes> GossipVerifiedBlob<T> {
     pub fn slot(&self) -> Slot {
         self.blob.message.slot
     }
+    pub fn index(&self) -> u64 {
+        self.blob.message.index
+    }
+    pub fn kzg_commitment(&self) -> KzgCommitment {
+        self.blob.message.kzg_commitment
+    }
     pub fn proposer_index(&self) -> u64 {
         self.blob.message.proposer_index
     }