Publish blockv2 ssz (#12636)

* wip produce block v2 ssz

* adding functions for ssz processing

* fixing linting

* Update beacon-chain/rpc/eth/beacon/handlers.go

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

* addressing review feedback

* fixing linting

---------

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

network/BUILD.bazel

@@ -6,6 +6,7 @@ go_library(
         "auth.go",
         "endpoint.go",
         "external_ip.go",
+        "reader.go",
         "writer.go",
     ],
     importpath = "github.com/prysmaticlabs/prysm/v4/network",
@@ -25,6 +26,7 @@ go_test(
         "auth_test.go",
         "endpoint_test.go",
         "external_ip_test.go",
+        "reader_test.go",
     ],
     embed = [":go_default_library"],
     deps = [