[jdk24u] RFR: 8346239: Improve memory efficiency of JimageDiffGenerator

[Severin Gehwolf]

Clean backport to improve diff generation.

-------------

Commit messages:
 - Backport f696d9c521fa13969cb81381dc8586bcdccf67d9

Changes: https://git.openjdk.org/jdk24u/pull/13/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk24u&pr=13&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8346239
  Stats: 77 lines in 16 files changed: 57 ins; 3 del; 17 mod
  Patch: https://git.openjdk.org/jdk24u/pull/13.diff
  Fetch: git fetch https://git.openjdk.org/jdk24u.git pull/13/head:pull/13

PR: https://git.openjdk.org/jdk24u/pull/13