HDDS-14350. Ratis configurations for ozone helm charts

[shuan1026]

What changes were proposed in this pull request?

Analyse Ratis configurations for handling network partitions / slow networks, covering Ratis timeouts, heartbeat settings, and leader election. This follows up on the HA Helm work in comment r2632023653.

• Adds ratis.ozoneSite to values.yaml: an empty map by default for optional ozone-site property overrides, with a curated, commented example list covering OM/SCM Ratis network-resilience timeouts and leader election.
• Renders ratis.ozoneSite entries as OZONE-SITE.XML_* env vars from ozone.configuration.env.common in _helpers.tpl, reusing the convention already used throughout the chart.

Curated keys documented as commented examples in values.yaml (any other ozone-site
property can also be set via this map):

• OM: ozone.om.ratis.server.request.timeout, ozone.om.ratis.minimum.timeout,
  ozone.om.ratis.server.failure.timeout.duration, ozone.om.ratis.server.leaderelection.pre-vote
• SCM: ozone.scm.ha.ratis.request.timeout, ozone.scm.ha.ratis.leader.election.timeout,
  ozone.scm.ha.raft.server.rpc.first-election.timeout,
  ozone.scm.ha.ratis.server.leaderelection.pre-vote,
  ozone.scm.ha.ratis.server.failure.timeout.duration

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-14350

How was this patch tested?

• Green CI run
• Manual verification:

# default: no ratis override env vars rendered
helm template test-release charts/ozone --show-only templates/om/om-statefulset.yaml | grep OZONE-SITE.XML_

# with overrides
cat > /tmp/ratis-override.yaml <<'EOF'
ratis:
  ozoneSite:
    ozone.om.ratis.server.request.timeout: "10s"
EOF
# expect:
#   - name: OZONE-SITE.XML_ozone.om.ratis.server.request.timeout
#     value: "10s"
helm template test-release charts/ozone -f /tmp/ratis-override.yaml \
  --show-only templates/om/om-statefulset.yaml \
  | grep -A1 'OZONE-SITE.XML_ozone.om.ratis.server.request.timeout'
  
# real cluster smoke test
kind create cluster --name ozone-helm-ratis
helm upgrade --install ozone charts/ozone --wait --timeout 15m
helm upgrade ozone charts/ozone -f /tmp/ratis-override.yaml --wait --timeout 15m
kubectl exec ozone-om-0 -- env | grep ratis.server.request.timeout

[shuan1026]

PTAL @adoroszlai @chungen0126 Thank you!