Use SSZ code from nim-ssz-serialization module (#875)

.gitmodules

@@ -193,3 +193,8 @@
   url = https://github.com/status-im/nim-websock
   ignore = dirty
   branch = master
+[submodule "vendor/nim-ssz-serialization"]
+	path = vendor/nim-ssz-serialization
+	url = https://github.com/status-im/nim-ssz-serialization.git
+	ignore = untracked
+	branch = master

fluffy/common/common_types.nim

@@ -8,7 +8,7 @@
 {.push raises: [Defect].}
 
 import
-  eth/ssz/ssz_serialization
+  ssz_serialization/types
 
 type
   ByteList* = List[byte, 2048]

fluffy/network/history/history_content.nim

@@ -12,7 +12,7 @@
 import
   std/options,
   nimcrypto/[sha2, hash], stew/objects, stint,
-  eth/ssz/ssz_serialization,
+  ssz_serialization,
   ../../common/common_types
 
 export ssz_serialization, common_types

fluffy/network/state/state_content.nim

@@ -12,7 +12,7 @@
 import
   std/options,
   nimcrypto/[sha2, hash], stew/objects, stint,
-  eth/ssz/ssz_serialization,
+  ssz_serialization,
   ../../common/common_types
 
 export ssz_serialization, common_types

fluffy/network/wire/messages.nim

@@ -13,7 +13,7 @@
 import
   std/options,
   stint, stew/[results, objects],
-  eth/ssz/ssz_serialization,
+  ssz_serialization,
   ../../common/common_types
 
 export ssz_serialization, stint, common_types
@@ -114,9 +114,6 @@ template messageKind*(T: typedesc[SomeMessage]): MessageKind =
 template toSszType*(x: UInt256): array[32, byte] =
   toBytesLE(x)
 
-template toSszType*(x: auto): auto =
-  x
-
 func fromSszBytes*(T: type UInt256, data: openArray[byte]):
     T {.raises: [MalformedSszError, Defect].} =
   if data.len != sizeof(result):

fluffy/network/wire/portal_protocol.nim

@@ -13,8 +13,8 @@
 import
   std/[sequtils, sets, algorithm],
   stew/results, chronicles, chronos, nimcrypto/hash,
+  ssz_serialization,
   eth/rlp, eth/p2p/discoveryv5/[protocol, node, enr, routing_table, random2, nodes_verification],
-  eth/ssz/ssz_serialization,
   ./messages
 
 export messages, routing_table

fluffy/tests/test_state_network.nim

@@ -8,7 +8,7 @@
 import
   std/os,
   testutils/unittests,
-  eth/[keys, trie/db, trie/hexary, ssz/ssz_serialization],
+  eth/[keys, trie/db, trie/hexary],
   eth/p2p/discoveryv5/protocol as discv5_protocol, eth/p2p/discoveryv5/routing_table,
   ../../nimbus/[genesis, chain_config, config, db/db_chain],
   ../network/wire/portal_protocol,

vendor/nim-ssz-serialization

@@ -0,0 +1 @@
+Subproject commit 5d65b20d6b56265902e5c9b6a2be4d1c2fd6427e