HDDS-15351. Display datanode UUID in Datanode web UI

[chihsuan]

What changes were proposed in this pull request?

This PR makes the DataNode web UI display the DataNode UUID.

Some operational commands (e.g. decommission) require the DataNode UUID, but previously there was no easy way to look it up from the web UI. This change exposes the UUID through the DataNode's JMX MXBean and renders it on the DataNode overview page.

Changes:

• DNMXBean / DNMXBeanImpl: add a datanodeUuid field with a getter/setter, following the existing hostName pattern. This exposes the UUID as the JMX attribute DatanodeUuid.
• HddsDatanodeService: during startup, set the UUID on the MXBean from datanodeDetails.getUuidString() (after the DataNode details are initialized, so the value is always present).
• overview.html (the shared framework overview template): add a Datanode UUID row, guarded by ng-if="$ctrl.jmx.DatanodeUuid" so it only renders on the DataNode UI. SCM/OM do not expose that JMX attribute, so the row is hidden there.

Note: the SCM web UI already shows the UUID (Node Status -> UUID column), so only the DataNode side needed changes here.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-15351

How was this patch tested?

Unit test: Added TestHddsDatanodeService#testDatanodeUuidInMXBean, which starts the service, reads the DatanodeUuid attribute from the JMX MXBean, and asserts it matches datanodeDetails.getUuidString().

Manual UI verification:

# from repo root
mvn clean install -DskipTests

cd hadoop-ozone/dist/target/ozone-*/compose/ozone
docker compose up -d --scale datanode=3

• DataNode UI (ports are dynamically mapped):

  docker compose ps datanode
  # or compose v2:
  docker compose port --index 1 datanode 19864

  Open the returned host/port (e.g. http://localhost:<mapped-port>). The overview table now shows the new row Datanode UUID.

[sreejasahithi]

Thanks @chihsuan for this improvement
LGTM