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/mc-pvc.yaml

@@ -0,0 +1,11 @@
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: {{ .Release.Name }}-mc-volume-claim
+spec:
+  accessModes:
+    - ReadWriteOnce
+  resources:
+    requests:
+      storage: {{ .Values.minecraft.resources.storage }}
+  storageClassName: longhorn