Route pgbouncer logs to virtio-serial (#9488)

virtio-serial is much more performant than /dev/console emulation,
therefore, is much more suitable for the verbose logs inside vm. This
commit changes routing for pgbouncer logs, since we've recently noticed
it can emit large volumes of logs.

Manually tested on staging by pinning a compute image to my test
project.

Should help with https://github.com/neondatabase/cloud/issues/19072

compute/vm-image-spec-bookworm.yaml

@@ -18,7 +18,7 @@ commands:
   - name: pgbouncer
     user: postgres
     sysvInitAction: respawn
-    shell: '/usr/local/bin/pgbouncer /etc/pgbouncer.ini'
+    shell: '/usr/local/bin/pgbouncer /etc/pgbouncer.ini 2>&1 > /dev/virtio-ports/tech.neon.log.0'
   - name: local_proxy
     user: postgres
     sysvInitAction: respawn

compute/vm-image-spec-bullseye.yaml

@@ -18,7 +18,7 @@ commands:
   - name: pgbouncer
     user: postgres
     sysvInitAction: respawn
-    shell: '/usr/local/bin/pgbouncer /etc/pgbouncer.ini'
+    shell: '/usr/local/bin/pgbouncer /etc/pgbouncer.ini 2>&1 > /dev/virtio-ports/tech.neon.log.0'
   - name: local_proxy
     user: postgres
     sysvInitAction: respawn