SSZ-QL: Add endpoints (BeaconState/BeaconBlock) (#15888)

* Move ssz_query objects into testing folder (ensuring test objects only used in test environment)

* Add containers for response

* Export sszInfo

* Add QueryBeaconState/Block

* Add comments and few refactor

* Fix merge conflict issues

* Return 500 when calculate offset fails

* Add test for QueryBeaconState

* Add test for QueryBeaconBlock

* Changelog :)

* Rename `QuerySSZRequest` to `SSZQueryRequest`

* Fix middleware hooks for RPC to accept JSON from client and return SSZ

* Convert to `SSZObject` directly from proto

* Move marshalling/calculating hash tree root part after `CalculateOffsetAndLength`

* Make nogo happy

* Add informing comment for using proto unsafe conversion

---------

Co-authored-by: Radosław Kapka <rkapka@wp.pl>

api/server/structs/endpoints_beacon.go

@@ -296,3 +296,8 @@ type GetBlobsResponse struct {
 	Finalized           bool     `json:"finalized"`
 	Data                []string `json:"data"` //blobs
 }
+
+type SSZQueryRequest struct {
+	Query        string `json:"query"`
+	IncludeProof bool   `json:"include_proof,omitempty"`
+}