fix: terminate pgbouncer on compute suspend (#12153)

## Problem

PgBouncer does not terminate connections on a suspend:
https://github.com/neondatabase/cloud/issues/16282

## Summary of changes

1. Adds a pid file to store the pid of PgBouncer
2. Terminates connections on a compute suspend

---------

Co-authored-by: Alexey Kondratov <kondratov.aleksey@gmail.com>

docker-compose/compute_wrapper/shell/compute.sh

@@ -95,3 +95,4 @@ echo "Start compute node"
      -b /usr/local/bin/postgres                              \
      --compute-id "compute-${RANDOM}"                          \
      --config "${CONFIG_FILE}"
+     --dev