Create a writeable /tmp directory

AI Gateway currently fails to start with the following error:

$ kubectl logs app-staging-bf8695cf5-2vqdv -n ai-gateway-eks
Error in tempfile() using template /tmp/parXXXXX.tst: Could not create temp file /tmp/parXZi0z.tst: Read-only file system at /usr/bin/parallel line 6309.

According to Configuring /tmp in a container we need to add the following to the Deployment:

volumes:
  - name: "tmp"
    emptyDir: {}

volumeMounts:
  - name: "tmp"
    mountPath: "/tmp"

To do

• Mount an emptyDir volume at /tmp
• Set the TMPDIR environment variable accordingly (optional but recommended)
• Update the Runway version used by AI Gateway to pick up this change