HBASE-29562 Add RegionServer Metrics for excluded DataNodes

[srinireddy2020]

Add and expose updated ‘ExcludeDNs’ information (with exclusion cause) to RegionServer metrics. This enhancement will allow operators and monitoring systems to track which DataNodes are excluded and understand the reasons directly through RS metrics, improving cluster observability and troubleshooting efficiency.

[Apache-HBase]

🎊 +1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 26s		Docker mode activated.
-0 ⚠️	yetus	0m 3s		Unprocessed flag(s): --brief-report-file --spotbugs-strict-precheck --author-ignore-list --blanks-eol-ignore-file --blanks-tabs-ignore-file --quick-hadoopcheck
			_ Prechecks _
			_ master Compile Tests _
+1 💚	mvninstall	3m 17s		master passed
+1 💚	compile	0m 14s		master passed
+1 💚	javadoc	0m 13s		master passed
+1 💚	shadedjars	6m 8s		branch has no errors when building our shaded downstream artifacts.
			_ Patch Compile Tests _
+1 💚	mvninstall	3m 8s		the patch passed
+1 💚	compile	0m 14s		the patch passed
+1 💚	javac	0m 14s		the patch passed
+1 💚	javadoc	0m 12s		the patch passed
+1 💚	shadedjars	6m 5s		patch has no errors when building our shaded downstream artifacts.
			_ Other Tests _
+1 💚	unit	0m 39s		hbase-hadoop-compat in the patch passed.
		21m 43s

Subsystem	Report/Notes
Docker	ClientAPI=1.43 ServerAPI=1.43 base: https://ci-hbase.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-7260/1/artifact/yetus-jdk17-hadoop3-check/output/Dockerfile
GITHUB PR	#7260
Optional Tests	javac javadoc unit compile shadedjars
uname	Linux ddc74d99b7f2 5.4.0-1103-aws #111~18.04.1-Ubuntu SMP Tue May 23 20:04:10 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/hbase-personality.sh
git revision	master / 3380d7b
Default Java	Eclipse Adoptium-17.0.11+9
Test Results	https://ci-hbase.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-7260/1/testReport/
Max. process+thread count	322 (vs. ulimit of 30000)
modules	C: hbase-hadoop-compat U: hbase-hadoop-compat
Console output	https://ci-hbase.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-7260/1/console
versions	git=2.34.1 maven=3.9.8
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[Apache-HBase]

🎊 +1 overall

Vote	Subsystem	Runtime	Logfile	Comment
+0 🆗	reexec	0m 28s		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 💚	hbaseanti	0m 0s		Patch does not have any anti-patterns.
			_ master Compile Tests _
+1 💚	mvninstall	3m 23s		master passed
+1 💚	compile	0m 22s		master passed
+1 💚	checkstyle	0m 10s		master passed
+1 💚	spotbugs	0m 25s		master passed
+1 💚	spotless	0m 50s		branch has no errors when running spotless:check.
			_ Patch Compile Tests _
+1 💚	mvninstall	3m 3s		the patch passed
+1 💚	compile	0m 21s		the patch passed
+1 💚	javac	0m 21s		the patch passed
+1 💚	blanks	0m 0s		The patch has no blanks issues.
-0 ⚠️	checkstyle	0m 8s	/results-checkstyle-hbase-hadoop-compat.txt	hbase-hadoop-compat: The patch generated 1 new + 1 unchanged - 0 fixed = 2 total (was 1)
+1 💚	spotbugs	0m 28s		the patch passed
+1 💚	hadoopcheck	12m 10s		Patch does not cause any errors with Hadoop 3.3.6 3.4.0.
+1 💚	spotless	0m 45s		patch has no errors when running spotless:check.
			_ Other Tests _
+1 💚	asflicense	0m 10s		The patch does not generate ASF License warnings.
		30m 24s

Subsystem	Report/Notes
Docker	ClientAPI=1.43 ServerAPI=1.43 base: https://ci-hbase.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-7260/1/artifact/yetus-general-check/output/Dockerfile
GITHUB PR	#7260
Optional Tests	dupname asflicense javac spotbugs checkstyle codespell detsecrets compile hadoopcheck hbaseanti spotless
uname	Linux 68d0ecf271eb 5.4.0-1103-aws #111~18.04.1-Ubuntu SMP Tue May 23 20:04:10 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
Build tool	maven
Personality	dev-support/hbase-personality.sh
git revision	master / 3380d7b
Default Java	Eclipse Adoptium-17.0.11+9
Max. process+thread count	81 (vs. ulimit of 30000)
modules	C: hbase-hadoop-compat U: hbase-hadoop-compat
Console output	https://ci-hbase.apache.org/job/HBase-PreCommit-GitHub-PR/job/PR-7260/1/console
versions	git=2.34.1 maven=3.9.8 spotbugs=4.7.3
Powered by	Apache Yetus 0.15.0 https://yetus.apache.org

This message was automatically generated.

[srinireddy2020]

@pankaj72981 please review this changes.