Add release notes for 2.10

[kotwanikunal]

Description

• Clear out changelog for released changes and adds in release notes for 2.10

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[github-actions]

Compatibility status:

Checks if related components are compatible with change 43af1d8

Incompatible components

Incompatible components: [https://github.com/opensearch-project/security.git]

Skipped components

Compatible components

Compatible components: [https://github.com/opensearch-project/alerting.git, https://github.com/opensearch-project/index-management.git, https://github.com/opensearch-project/sql.git, https://github.com/opensearch-project/anomaly-detection.git, https://github.com/opensearch-project/job-scheduler.git, https://github.com/opensearch-project/asynchronous-search.git, https://github.com/opensearch-project/observability.git, https://github.com/opensearch-project/common-utils.git, https://github.com/opensearch-project/k-nn.git, https://github.com/opensearch-project/reporting.git, https://github.com/opensearch-project/cross-cluster-replication.git, https://github.com/opensearch-project/security-analytics.git, https://github.com/opensearch-project/custom-codecs.git, https://github.com/opensearch-project/performance-analyzer.git, https://github.com/opensearch-project/ml-commons.git, https://github.com/opensearch-project/opensearch-oci-object-storage.git, https://github.com/opensearch-project/performance-analyzer-rca.git, https://github.com/opensearch-project/geospatial.git, https://github.com/opensearch-project/notifications.git, https://github.com/opensearch-project/neural-search.git]

[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: UNSTABLE ❕
• TEST FAILURES:

      1 org.opensearch.cluster.allocation.ClusterRerouteIT.testDelayWithALargeAmountOfShards

• URL: https://build.ci.opensearch.org/job/gradle-check/25225/
• CommitID: 43af1d8
  Please review all flaky tests that succeeded after retry and create an issue if one does not already exist to track the flaky failure.

[codecov]

Codecov Report

Merging #9955 (43af1d8) into main (5c3d26d) will decrease coverage by 0.03%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##               main    #9955      +/-   ##
============================================
- Coverage     71.16%   71.13%   -0.03%     
- Complexity    58087    58093       +6     
============================================
  Files          4824     4824              
  Lines        273897   273897              
  Branches      39910    39910              
============================================
- Hits         194909   194844      -65     
- Misses        62681    62691      +10     
- Partials      16307    16362      +55     

see 485 files with indirect coverage changes