Suricata

Add initial support for PostgreSQL's CopyBoth mode, in which a backend in walsender mode executes a START_REPLICATION statement.

The backend sends a CopyBothResponse message to the frontend. Both the backend and the frontend may then send CopyData messages until either end sends a CopyDone message.
This may happen in simple query or extended mode/ subprotocol, too, although extended query mode isn't covered by the pgsql app-layer yet.

PostgreSQL's protocol has a so-called Copy subprotocol.

The COPY operations can be split into three different modes (cf https://www.postgresql.org/docs/13/protocol-flow.html#PROTOCOL-COPY):
- Copy-In mode - high-speed bulk data transfer to the server
- Copy-Out mode - high-speed bulk data transfer from the server
- Copy-Both - high-speed bulk data transfer to and from the server