Dávid Paksy

This is a backport of https://github.com/apache/hbase/pull/6875 to `branch-2.5`. Cherry-picked the `branch-2` patch (https://github.com/apache/hbase/pull/7478). The reason is that in `branch-2`, `branch-2.6` and `branch-2.5` there is no `org.apache.hadoop.hbase.rsgroup.RSGroupUtil` or `RSGroupInfoManager` and also...

### Testing Tested this the same way, as I did for the master version: - https://github.com/apache/hbase/pull/6875#issuecomment-2772712499 - https://github.com/apache/hbase/pull/6875#issuecomment-3196152945

> Hi @PDavid, can you please review this PR? Also, I am still having trouble getting the HBase UI to work locally, so I have not been able to manually...

> Hi @PDavid, it turned out there is a compatibility issue with Hadoop versions older than Hadoop 3.4. [YARN-11308](https://issues.apache.org/jira/browse/YARN-11308) introduced the new [Configuration.writeXml()](https://github.com/apache/hadoop/blob/branch-3.4.2/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/Configuration.java#L3622) method that I was using in my...

Thanks @kgeisz for this fix, I now merged this to master branch. Can you please prepare a backport PR for `branch-2`?

> @PDavid, I spoke with @taklwu. I will backport to branch-2, branch-2.6, and branch-3. Great, many thanks @kgeisz! :+1: