RFR: 8361325: Refactor ClassLoaderExt

[Calvin Cheung]

After the refactoring work done via [JDK-8280682](https://bugs.openjdk.org/browse/JDK-8280682), there are only three functions remaining in the ClassLoaderExt class. This RFE is to move those remaining functions into other classes so that the ClassLoaderExt class can be eliminated.

Testing: passed tiers 1 - 5.

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Commit messages:
 - 8361325: Refactor ClassLoaderExt

Changes: https://git.openjdk.org/jdk/pull/26110/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26110&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8361325
  Stats: 228 lines in 15 files changed: 59 ins; 165 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/26110.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26110/head:pull/26110

PR: https://git.openjdk.org/jdk/pull/26110