RFR: 8238: Update to Eclipse 2024-06

[Marcus Hirt]

This one got a bit interesting.

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Commit messages:
 - Updating to the correct spifly version in the 2024-03 target
 - Getting the right maven version
 - Updating action versions
 - Using both the JDK 17 toolchain (for core) and JDK 21 (for the app)
 - Updating to 21, and updating the platform definition with the additional jolokia dependencies
 - Updating HDR histogram
 - Merge branch 'openjdk:master' into 8238-update-2024-06
 - Merge pull request #3 from viragpurnam/8238-Working
 - 8238 JDK 21
 - 8238 JDK 21
 - ... and 5 more: https://git.openjdk.org/jmc/compare/4c9d9e47...2b468857

Changes: https://git.openjdk.org/jmc/pull/578/files
  Webrev: https://webrevs.openjdk.org/?repo=jmc&pr=578&range=00
  Issue: https://bugs.openjdk.org/browse/JMC-8238
  Stats: 345 lines in 9 files changed: 299 ins; 21 del; 25 mod
  Patch: https://git.openjdk.org/jmc/pull/578.diff
  Fetch: git fetch https://git.openjdk.org/jmc.git pull/578/head:pull/578

PR: https://git.openjdk.org/jmc/pull/578