Initialize the ExecutionRequests field in gossip block map (#16047)

**What type of PR is this?**

Other

**What does this PR do? Why is it needed?**

When unmarshaling a block with fastssz, if the target block's
`ExecutionRequests` field is nil, it will not get populated
```
if b.ExecutionRequests == nil {
	b.ExecutionRequests = new(v1.ExecutionRequests)
}
if err = b.ExecutionRequests.UnmarshalSSZ(buf); err != nil {
	return err
}
```
This is true for other fields and that's why we initialize them in our
gossip data maps. There is no bug at the moment because even if
execution requests are nil, we initialize them in
`consensus-types/blocks/proto.go`
```
er := pb.ExecutionRequests
if er == nil {
	er = &enginev1.ExecutionRequests{}
}
```
However, since we initialize other fields in the data map, it's safer to
do it for execution requests too, to avoid a bug in case the code in
`consensus-types/blocks/proto.go` changes in the future.

**Acknowledgements**

- [x] I have read
[CONTRIBUTING.md](https://github.com/prysmaticlabs/prysm/blob/develop/CONTRIBUTING.md).
- [x] I have included a uniquely named [changelog fragment
file](https://github.com/prysmaticlabs/prysm/blob/develop/CONTRIBUTING.md#maintaining-changelogmd).
- [x] I have added a description to this PR with sufficient context for
reviewers to understand this PR.

Author: rkapka

beacon-chain/p2p/types/object_mapping.go

@@ -77,12 +77,12 @@ func InitializeDataMaps() {
 		},
 		bytesutil.ToBytes4(params.BeaconConfig().ElectraForkVersion): func() (interfaces.ReadOnlySignedBeaconBlock, error) {
 			return blocks.NewSignedBeaconBlock(
-				&ethpb.SignedBeaconBlockElectra{Block: &ethpb.BeaconBlockElectra{Body: &ethpb.BeaconBlockBodyElectra{ExecutionPayload: &enginev1.ExecutionPayloadDeneb{}}}},
+				&ethpb.SignedBeaconBlockElectra{Block: &ethpb.BeaconBlockElectra{Body: &ethpb.BeaconBlockBodyElectra{ExecutionPayload: &enginev1.ExecutionPayloadDeneb{}, ExecutionRequests: &enginev1.ExecutionRequests{}}}},
 			)
 		},
 		bytesutil.ToBytes4(params.BeaconConfig().FuluForkVersion): func() (interfaces.ReadOnlySignedBeaconBlock, error) {
 			return blocks.NewSignedBeaconBlock(
-				&ethpb.SignedBeaconBlockFulu{Block: &ethpb.BeaconBlockElectra{Body: &ethpb.BeaconBlockBodyElectra{ExecutionPayload: &enginev1.ExecutionPayloadDeneb{}}}},
+				&ethpb.SignedBeaconBlockFulu{Block: &ethpb.BeaconBlockElectra{Body: &ethpb.BeaconBlockBodyElectra{ExecutionPayload: &enginev1.ExecutionPayloadDeneb{}, ExecutionRequests: &enginev1.ExecutionRequests{}}}},
 			)
 		},
 	}

changelog/radek_init-gossip-execution-requests.md

@@ -0,0 +1,3 @@
+### Changed
+
+- Initialize the `ExecutionRequests` field in gossip block map.