Backport JDK-8037914 (JFR event for string deduplication) to sapmachine25

[parttimenerd]

Backport the new jdk.StringDeduplication JFR event to sapmachine25.

Upstream:

• JDK-8037914 "Add JFR event for string deduplication" (3a2845f)
• JDK-8372348 "Adjust some UL / JFR string deduplication output messages" (3f20eb9)

The event exposes per-cycle concurrent string-deduplication statistics (inspected/known/shared/new/deduplicated counts and bytes, skipped dead/incomplete/shared, and processing/table-resize/table-cleanup timings) under category "Java Virtual Machine, GC, Detailed". This enables consuming string-dedup metrics via JFR instead of only -Xlog:stringdedup.