RFR: 8374045: Add support to run benchmarking with fragmented CodeCache [v2]

[Chad Rakoczy]

> [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.

Chad Rakoczy has updated the pull request incrementally with one additional commit since the last revision:

  Update rng

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Changes:
  - all: https://git.openjdk.org/jdk/pull/28934/files
  - new: https://git.openjdk.org/jdk/pull/28934/files/c2108d55..f40ad8c1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28934&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28934&range=00-01

  Stats: 18 lines in 2 files changed: 2 ins; 5 del; 11 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