Merge #4163

4163: Change network policy label for the update proposals/votes and heavyweight delegation certificates r=disassembler a=dcoutts

## Description

The update proposals and votes, and the heavyweight delegation certificates are currently labelled as MsgTransaction for the purpose of the network routing policy.

This means we can currently submit such objects from any node and they will be forwarded to the core nodes. They are of course validated at every hop.

For the purpose of the byron/shelley transition it will be simpler if these objects are only submitted directly to the federated core nodes and not via the relays.

So this patch changes the policy so that these objects are not forwarded by the relays. It does this by changing their label so that the existing network routing policy treats them differently. So rather than being
labelled as `MsgTransaction` they are labelled as `MsgMPC`. The existing policy for the MPC label is that relays do not forward such messages.

## Linked issue

[CBR-526](https://iohk.myjetbrains.com/youtrack/issue/CBR-526)



Co-authored-by: Duncan Coutts <[email protected]>

Author: iohk-bors[bot]

lib/src/Pos/Diffusion/Full/Delegation.hs

@@ -49,7 +49,7 @@ pskHeavyRelay
     :: Logic IO
     -> Relay
 pskHeavyRelay logic = Data $ DataParams
-    MsgTransaction
+    MsgMPC
     (\_ _ -> postPskHeavy logic)
     -- The message size limit for ProxySKHeavy: a ProxySecretKey with an
     -- EpochIndex.
@@ -60,4 +60,4 @@ sendPskHeavy
     -> EnqueueMsg
     -> ProxySKHeavy
     -> IO ()
-sendPskHeavy logTrace enqueue = dataFlow logTrace "pskHeavy" enqueue (MsgTransaction OQ.OriginSender)
+sendPskHeavy logTrace enqueue = dataFlow logTrace "pskHeavy" enqueue (MsgMPC OQ.OriginSender)

lib/src/Pos/Diffusion/Full/Update.hs

@@ -85,7 +85,7 @@ proposalRelay logic =
     InvReqData
         NoMempool $
         InvReqDataParams
-           { invReqMsgType = MsgTransaction
+           { invReqMsgType = MsgMPC
            , contentsToKey = KV.toKey kv
            , handleInv = \_ -> KV.handleInv kv
            , handleReq = \_ -> KV.handleReq kv
@@ -104,7 +104,7 @@ voteRelay logic =
     InvReqData
         NoMempool $
         InvReqDataParams
-           { invReqMsgType = MsgTransaction
+           { invReqMsgType = MsgMPC
            , contentsToKey = KV.toKey kv
            , handleInv = \_ -> KV.handleInv kv
            , handleReq = \_ -> KV.handleReq kv