[JDK-8374045](https://bugs.openjdk.org/browse/JDK-8374045)
This PR adds a new utility tool CodeCacheFragmenter to help with testing HotSpot code cache fragmentation scenarios. The tool is a Java agent that uses the WhiteBox API to create and randomly free dummy code blobs in the NonProfiled code heap to achieve a specified fill percentage. It includes configurable parameters for blob sizes, target fill percentage (0-100%), and random seeding to enable reproducible fragmentation patterns. The utility is built via a standard Makefile and produces `codecachefragmenter.jar` which can be used as a Java agent with `-javaagent` flag. This tool is intended for performance testing and experimentation with code cache behavior under various fragmentation conditions. This is useful to show the performance benefits of [JDK-8326205](https://bugs.openjdk.org/browse/JDK-8326205) With the same amount of free code cache memory, adding fragmentation increases execution time of Renaissance Dotty by ~5x. See https://github.com/openjdk/jdk/pull/28934#issuecomment-3820151693 for more details. ------------- Commit messages: - Merge remote-tracking branch 'origin/master' into CodeCacheFragAgent - Small improvements - Make README markdown - Implement build system - Add CodeCacheFragAgent Changes: https://git.openjdk.org/jdk/pull/28934/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28934&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8374045 Stats: 331 lines in 5 files changed: 331 ins; 0 del; 0 mod Patch: https://git.openjdk.org/jdk/pull/28934.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/28934/head:pull/28934 PR: https://git.openjdk.org/jdk/pull/28934
