feat: split sid into two fields, use map for vector clock

proto/xmtpv4/message_api/message_api.proto

@@ -13,7 +13,7 @@ option go_package = "github.com/xmtp/proto/v3/go/xmtpv4/message_api";
 // The last seen entry per originator. Originators that have not been seen are omitted.
 // Entries MUST be sorted in ascending order, so that smaller node ID's appear first.
 message VectorClock {
-  repeated uint64 originator_sids = 1;
+  map<uint32, uint64> node_id_to_sequence_id = 1;
 }
 
 // Data visible to the server that has been authenticated by the client.
@@ -42,15 +42,16 @@ message PayerEnvelope {
 // For blockchain envelopes, the originator_sid is set by the smart contract,
 // but the originator_ns is set by the publishing node
 message UnsignedOriginatorEnvelope {
-  uint64 originator_sid = 1;
-  int64 originator_ns = 2;
-  PayerEnvelope payer_envelope = 3;
+  uint32 originator_node_id = 1;
+  uint64 originator_sequence_id = 2;
+  int64 originator_ns = 3;
+  PayerEnvelope payer_envelope = 4;
 }
 
 // An alternative to a signature for blockchain payloads
 message BlockchainProof {
   uint64 block_number = 1;
-  uint32 publisher_id = 2;
+  uint32 publisher_node_id = 2;
 }
 
 // Signed originator envelope