easy smokescreen address whitelist

[aogier]

This PR helped me solving the problem we face with smokescreen when some of your services are on a private network. Entirely disabling it does not looks like a good idea, plus I did not manage to do that because everything broke when I added the usual:

[proxy]
host = 

thing. So! This uses dockerfile's entrypoint runPostSetupScripts and allows me to list my whitelisted addressed so everything works well!

How did you test this PR?

$ diff -u \
 <(helm template zulip . -s templates/cm-post-setup-scripts.yaml) \
 <(helm template zulip . \
      --set-json=zulip.smokeScreen.whitelistedAddresses='["1.2.3.4", "11.22.33.44"]' \
      -s templates/cm-post-setup-scripts.yaml)
--- /proc/self/fd/11    2024-12-28 15:55:37.660000000 +0100
+++ /proc/self/fd/22    2024-12-28 15:55:37.660000000 +0100
@@ -11,3 +11,9 @@
     app.kubernetes.io/version: "9.3-0"
     app.kubernetes.io/managed-by: Helm
 data:
+  __zulip_smokescreen_whitelist.sh: |
+    #!/bin/bash
+
+    sed -ri \
+        "s/(command.*)/\1 --allow-address 1.2.3.4 --allow-address 11.22.33.44/" \
+        /etc/supervisor/conf.d/zulip/smokescreen.conf

Hope this helps, ciao!