RFR: 8265602: -XX:DumpLoadedClassList should support custom loaders [v2]

[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

Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:

  @calvinccheung comments

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4952/files
  - new: https://git.openjdk.java.net/jdk/pull/4952/files/ca7ba80d..04ae4859

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4952&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4952&range=00-01

  Stats: 4 lines in 3 files changed: 2 ins; 1 del; 1 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