Import minecraft-server chart for Fleet migration stage 1 (java8 line)

Imports the chart from cluster-config functionally unchanged, wires it into
the publish/validate/install-test pipelines and publishes it as the first of
three Java lines (0.4.0+upjava8).

The only deviation from the source chart is the chart-global scaleDown flag
plus a server.replicas value, following the satisfactory pattern: two of the
three servers stand at 0 replicas in the cluster, which the chart could not
express, and Fleet would otherwise start them on reconcile. The default
(scaleDown: false) still renders replicas: 1, so the rendering of the running
server is unchanged - verified byte-identical against the three real values
files for all three Java lines.

Known deficiencies (hardening, probes, naming scheme, hardcoded values,
missing icon, the misleading mc-router auto-discovery annotations) are left
untouched on purpose and are scheduled for stage 2.

minecraft-server/templates/init-script-configmap.yaml

@@ -0,0 +1,42 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: {{ .Release.Name }}-init-config
+data:
+  init.sh: |
+    echo "downloading serverpack"
+    wget -O /modpacks/serverpack.zip {{ .Values.curseforgeServerpack.downloadUrl }}
+    SERVERPACK_DIR="{{ .Values.curseforgeServerpack.workingDirectory }}"
+    BACKUP_DIR="/data/serverpack-backup"
+
+    if [ -d "$SERVERPACK_DIR" ]; then
+      echo "found installed server. Migrating..."
+      if [ -d "$BACKUP_DIR" ]; then
+        echo "clearing old Backup"
+        rm -rf $BACKUP_DIR
+      fi
+
+      echo "backing up old server-files"
+      cp -r $SERVERPACK_DIR $BACKUP_DIR
+
+      rm -rf $SERVERPACK_DIR
+      mkdir $SERVERPACK_DIR
+
+      echo "extracting new server-files"
+      tar -xvf /modpacks/serverpack.zip -C $SERVERPACK_DIR
+
+      echo "copying old configuration-data"
+      cp -r $BACKUP_DIR/world $SERVERPACK_DIR/world
+      cp $BACKUP_DIR/banned-ips.json $SERVERPACK_DIR/banned-ips.json
+      cp $BACKUP_DIR/banned-players.json $SERVERPACK_DIR/banned-players.json
+      cp $BACKUP_DIR/ops.json $SERVERPACK_DIR/ops.json
+      cp $BACKUP_DIR/whitelist.json $SERVERPACK_DIR/whitelist.json
+
+      echo "change owner of files"
+      chown -R 1000:1000 $SERVERPACK_DIR
+
+      echo "successfully migrated server"
+
+      # echo "deleting serverpack.zip"
+      # rm /modpacks/serverpack.zip
+    fi