Create opensearch-performance-analyzer.release-notes-2.15.0.0.md (#1) (…

…#671) (#672)

(cherry picked from commit 9cb092f)

Co-authored-by: DevJhaAbhishek <137988638+DevJhaAbhishek@users.noreply.github.com>

release-notes/release-notes/opensearch-performance-analyzer.release-notes-2.15.0.0.md

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+## Version 2.15.0 Release Notes
+
+Compatible with OpenSearch 2.15.0
+
+### Infrastructure
+* Bump PA to use 1.4.0 PA commons lib [#664](https://github.com/opensearch-project/performance-analyzer/pull/664)
+
+### Feature 
+* Framework changes to merge PA with RTF [#662](https://github.com/opensearch-project/performance-analyzer/pull/662)
+
+### Bug Fix
+* Fixed the bug in CacheConfigMetricsCollector [#657](https://github.com/opensearch-project/performance-analyzer/pull/657)