Add NormalUnderReplBlocksCount and BadlyDistributedBlocksCount to getStats() NN RPC

[aswinmprabhu]

Description of PR

At LinkedIn, we use the stats from the getStats() NN RPC call to evaluate safety checks that ensure that various maintenance ops are safe to run.

Due to a migration we are undertaking, the badly distributed block count is very high for the cluster undergoing migration. This is not a safety problem. However, to distinguish it from the actual low redundancy block count, we need both these values to be available from the getStats() RPC. The current low redundancy blocks count value available is the sum of all the different types of low redundancy blocks, including normal low redundancy blocks and badly distributed blocks.

This PR adds these 2 values separately to the array returned by getStats() RPC.

How was this patch tested?

Trivial change. It has been running in our prod cluster for a bit now.
Build passes:

[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  42:50 min
[INFO] Finished at: 2025-05-19T14:51:09+05:30
[INFO] ------------------------------------------------------------------------

For code changes:

• Does the title or this PR starts with the corresponding JIRA issue id (e.g. 'HADOOP-17799. Your PR title ...')?
• Object storage: have the integration tests been executed and the endpoint declared according to the connector-specific documentation?
• If adding new dependencies to the code, are these dependencies licensed in a way that is compatible for inclusion under ASF 2.0?
• If applicable, have you updated the LICENSE, LICENSE-binary, NOTICE-binary files?

[hadoop-yetus]

💔 -1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	7m 21s		Docker mode activated.
			_ Prechecks _
+1 💚	dupname	0m 0s		No case conflicting files found.
+0 🆗	codespell	0m 0s		codespell was not available.
+0 🆗	detsecrets	0m 0s		detect-secrets was not available.
+1 💚	@author	0m 0s		The patch does not contain any @author tags.
-1 ❌	test4tests	0m 0s		The patch doesn't appear to include any new or modified tests. Please justify why no new tests are needed for this patch. Also please list what manual steps were performed to verify this patch.
			_ trunk Compile Tests _
+0 🆗	mvndep	10m 39s		Maven dependency ordering for branch
+1 💚	mvninstall	47m 47s		trunk passed
+1 💚	compile	7m 11s		trunk passed with JDK Ubuntu-11.0.27+6-post-Ubuntu-0ubuntu120.04
+1 💚	compile	6m 33s		trunk passed with JDK Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
+1 💚	checkstyle	1m 38s		trunk passed
+1 💚	mvnsite	2m 23s		trunk passed
+1 💚	javadoc	2m 0s		trunk passed with JDK Ubuntu-11.0.27+6-post-Ubuntu-0ubuntu120.04
+1 💚	javadoc	2m 18s		trunk passed with JDK Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
+1 💚	spotbugs	5m 43s		trunk passed
+1 💚	shadedclient	44m 10s		branch has no errors when building and testing our client artifacts.
			_ Patch Compile Tests _
+0 🆗	mvndep	0m 34s		Maven dependency ordering for patch
+1 💚	mvninstall	1m 56s		the patch passed
+1 💚	compile	6m 25s		the patch passed with JDK Ubuntu-11.0.27+6-post-Ubuntu-0ubuntu120.04
+1 💚	javac	6m 25s		the patch passed
+1 💚	compile	5m 40s		the patch passed with JDK Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
+1 💚	javac	5m 40s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
-0 ⚠️	checkstyle	1m 18s	/results-checkstyle-hadoop-hdfs-project.txt	hadoop-hdfs-project: The patch generated 1 new + 169 unchanged - 0 fixed = 170 total (was 169)
+1 💚	mvnsite	2m 1s		the patch passed
-1 ❌	javadoc	0m 38s	/results-javadoc-javadoc-hadoop-hdfs-project_hadoop-hdfs-client-jdkUbuntu-11.0.27+6-post-Ubuntu-0ubuntu120.04.txt	hadoop-hdfs-project_hadoop-hdfs-client-jdkUbuntu-11.0.27+6-post-Ubuntu-0ubuntu120.04 with JDK Ubuntu-11.0.27+6-post-Ubuntu-0ubuntu120.04 generated 4 new + 1161 unchanged - 0 fixed = 1165 total (was 1161)
+1 💚	javadoc	2m 7s		the patch passed with JDK Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
+1 💚	spotbugs	5m 55s		the patch passed
+1 💚	shadedclient	47m 21s		patch has no errors when building and testing our client artifacts.
			_ Other Tests _
+1 💚	unit	2m 44s		hadoop-hdfs-client in the patch passed.
+1 💚	unit	309m 14s		hadoop-hdfs in the patch passed.
+1 💚	asflicense	1m 36s		The patch does not generate ASF License warnings.
		526m 7s

Subsystem	Report/Notes
Docker	ClientAPI=1.51 ServerAPI=1.51 base: https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-7963/1/artifact/out/Dockerfile
GITHUB PR	#7963
Optional Tests	dupname asflicense compile javac javadoc mvninstall mvnsite unit shadedclient spotbugs checkstyle codespell detsecrets
uname	Linux ff8876321817 5.15.0-143-generic #153-Ubuntu SMP Fri Jun 13 19:10:45 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/bin/hadoop.sh
git revision	trunk / 20f5e88
Default Java	Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
Multi-JDK versions	/usr/lib/jvm/java-11-openjdk-amd64:Ubuntu-11.0.27+6-post-Ubuntu-0ubuntu120.04 /usr/lib/jvm/java-8-openjdk-amd64:Private Build-1.8.0_452-8u452-gaus1-0ubuntu120.04-b09
Test Results	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-7963/1/testReport/
Max. process+thread count	2422 (vs. ulimit of 5500)
modules	C: hadoop-hdfs-project/hadoop-hdfs-client hadoop-hdfs-project/hadoop-hdfs U: hadoop-hdfs-project
Console output	https://ci-hadoop.apache.org/job/hadoop-multibranch/job/PR-7963/1/console
versions	git=2.25.1 maven=3.6.3 spotbugs=4.2.2
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