ci: pull redpanda from its own registry and give it a longer health window

Two things tripped up the first CI run on developer/arr2036:

 - The ci.yml and ci-sanitizers.yml workflows pulled redpanda through
   the FreeRADIUS internal docker mirror (docker.internal.networkradius.com),
   but redpandadata/redpanda is not mirrored there, so every job with a
   redpanda service container died at 'Initialize containers'.  Pull
   directly from docker.redpanda.com, matching what the multi-server
   docker-compose already does.

 - The multi-server redpanda service had a 60s start window and 30s of
   retries.  On a busy self-hosted runner that's marginal - we saw
   kafka-produce-short_ci fail the compose-up health gate.  Bump the
   start_period to 120s and extend retries so we allow up to ~4 minutes
   for the broker to come up.

Author: arr2036

.github/workflows/ci-sanitizers.yml

@@ -128,8 +128,12 @@ jobs:
           --health-timeout 5s
           --health-retries 5
 
+      #
+      #  Pulled from docker.redpanda.com rather than the FreeRADIUS internal
+      #  docker cache because redpandadata/redpanda is not mirrored there.
+      #
       redpanda:
-        image: ${{ needs.pre-ci.outputs.docker_prefix }}redpandadata/redpanda:latest
+        image: docker.redpanda.com/redpandadata/redpanda:latest
         ports:
           - 9092:9092
         options: >-

.github/workflows/ci.yml

@@ -139,8 +139,12 @@ jobs:
       #  on port 9092.  No setup script is needed: librdkafka auto-creates the
       #  test topics on first produce.
       #
+      #  Pulled from docker.redpanda.com rather than the FreeRADIUS internal
+      #  docker cache because redpandadata/redpanda is not mirrored there.
+      #  Matches the image used by the multi-server test harness.
+      #
       redpanda:
-        image: ${{ needs.pre-ci.outputs.docker_prefix }}redpandadata/redpanda:latest
+        image: docker.redpanda.com/redpandadata/redpanda:latest
         ports:
           - 9092:9092
         options: >-

src/tests/multi-server/environments/kafka.yml.j2

@@ -50,12 +50,19 @@ services:
     - --check=false
     - --unsafe-bypass-fsync=true
     restart: unless-stopped
+    #
+    #  Redpanda needs longer than you'd think on a busy CI runner: the
+    #  first-launch data directory scaffolding can take 30-60s before
+    #  rpk admin is reachable, and the cluster-health probe only returns
+    #  OK once the controller topic has settled.  Give it up to ~4 min
+    #  before declaring the container unhealthy.
+    #
     healthcheck:
       test: ["CMD-SHELL", "rpk cluster health --exit-when-healthy"]
-      interval: 2s
-      timeout: 5s
-      retries: 15
-      start_period: 60s
+      interval: 5s
+      timeout: 10s
+      retries: 24
+      start_period: 120s
 
   kafka-producer1:
     image: freeradius-build:latest