add ssz support in request body for /beacon/blocks endpoints (v1 & v2) (#4479)

## Issue Addressed

[#4457](https://github.com/sigp/lighthouse/issues/4457)

## Proposed Changes

add ssz support in request body for  /beacon/blocks endpoints (v1 & v2)


## Additional Info

beacon_node/http_api/tests/broadcast_validation_tests.rs

@@ -175,6 +175,48 @@ pub async fn gossip_full_pass() {
         .block_is_known_to_fork_choice(&block.canonical_root()));
 }
 
+// This test checks that a block that is valid from both a gossip and consensus perspective is accepted when using `broadcast_validation=gossip`.
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+pub async fn gossip_full_pass_ssz() {
+    /* this test targets gossip-level validation */
+    let validation_level: Option<BroadcastValidation> = Some(BroadcastValidation::Gossip);
+
+    // Validator count needs to be at least 32 or proposer boost gets set to 0 when computing
+    // `validator_count // 32`.
+    let validator_count = 64;
+    let num_initial: u64 = 31;
+    let tester = InteractiveTester::<E>::new(None, validator_count).await;
+
+    // Create some chain depth.
+    tester.harness.advance_slot();
+    tester
+        .harness
+        .extend_chain(
+            num_initial as usize,
+            BlockStrategy::OnCanonicalHead,
+            AttestationStrategy::AllValidators,
+        )
+        .await;
+    tester.harness.advance_slot();
+
+    let slot_a = Slot::new(num_initial);
+    let slot_b = slot_a + 1;
+
+    let state_a = tester.harness.get_current_state();
+    let (block, _): (SignedBeaconBlock<E>, _) = tester.harness.make_block(state_a, slot_b).await;
+
+    let response: Result<(), eth2::Error> = tester
+        .client
+        .post_beacon_blocks_v2_ssz(&block, validation_level)
+        .await;
+
+    assert!(response.is_ok());
+    assert!(tester
+        .harness
+        .chain
+        .block_is_known_to_fork_choice(&block.canonical_root()));
+}
+
 /// This test checks that a block that is **invalid** from a gossip perspective gets rejected when using `broadcast_validation=consensus`.
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 pub async fn consensus_invalid() {

beacon_node/http_api/tests/tests.rs

@@ -1247,6 +1247,22 @@ impl ApiTester {
         self
     }
 
+    pub async fn test_post_beacon_blocks_ssz_valid(mut self) -> Self {
+        let next_block = &self.next_block;
+
+        self.client
+            .post_beacon_blocks_ssz(next_block)
+            .await
+            .unwrap();
+
+        assert!(
+            self.network_rx.network_recv.recv().await.is_some(),
+            "valid blocks should be sent to network"
+        );
+
+        self
+    }
+
     pub async fn test_post_beacon_blocks_invalid(mut self) -> Self {
         let block = self
             .harness
@@ -1270,6 +1286,29 @@ impl ApiTester {
         self
     }
 
+    pub async fn test_post_beacon_blocks_ssz_invalid(mut self) -> Self {
+        let block = self
+            .harness
+            .make_block_with_modifier(
+                self.harness.get_current_state(),
+                self.harness.get_current_slot(),
+                |b| {
+                    *b.state_root_mut() = Hash256::zero();
+                },
+            )
+            .await
+            .0;
+
+        assert!(self.client.post_beacon_blocks_ssz(&block).await.is_err());
+
+        assert!(
+            self.network_rx.network_recv.recv().await.is_some(),
+            "gossip valid blocks should be sent to network"
+        );
+
+        self
+    }
+
     pub async fn test_beacon_blocks(self) -> Self {
         for block_id in self.interesting_block_ids() {
             let expected = block_id
@@ -4451,6 +4490,22 @@ async fn post_beacon_blocks_valid() {
     ApiTester::new().await.test_post_beacon_blocks_valid().await;
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn post_beacon_blocks_ssz_valid() {
+    ApiTester::new()
+        .await
+        .test_post_beacon_blocks_ssz_valid()
+        .await;
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_post_beacon_blocks_ssz_invalid() {
+    ApiTester::new()
+        .await
+        .test_post_beacon_blocks_ssz_invalid()
+        .await;
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn post_beacon_blocks_invalid() {
     ApiTester::new()