RFR: 8265602: -XX:DumpLoadedClassList should support custom loaders

[Ioi Lam]

Some applications load a lot of classes using custom loaders. This PR improves the start-up performance of these apps when using a "static" CDS archive:

Here are performance numbers for the Eclipse IDE:


Static Archive Before: 7.31 sec (classlist does not include custom loader classes)
Static Archive After:  6.49 sec (classlist includes custom loader classes)
Dynamic Archive:       6.62 sec

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Commit messages:
 - 8265602: -XX:DumpLoadedClassList should support custom loaders

Changes: https://git.openjdk.java.net/jdk/pull/4952/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4952&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8265602
  Stats: 681 lines in 15 files changed: 500 ins; 135 del; 46 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4952.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4952/head:pull/4952

PR: https://git.openjdk.java.net/jdk/pull/4952