encode before incrementing seq + putting in send buffer

[jackyzha0]

Why + What changed

spiritual successor of #278

• Moves message encoding (codec.toBuffer) before incrementing the sequence number and pushing to the send buffer, so that if encoding fails (e.g. unserializable values like Symbol), or JS cannot allocate memory for the buffer, the session seq doesn't get out of sync
• Changes the send buffer type from OpaqueTransportMessage[] to EncodedTransportMessage[] so buffered messages are already serialized and don't need re-encoding on
  reconnect
• Adds tests for unserializable values in procedure handlers (binary codec throws, JSON codec silently drops)

Versioning

• Breaking protocol change
• Breaking ts/js API change

[peter-zhong-replit]

remove earlier accidental stamp

remove rquest changes