RFR: 8317692: jcmd GC.heap_dump performance regression after JDK-8292818 [v4]

[Hannes Greule]

> See the bug description for more information.
> 
> This implementation brings down the time to take a heap dump on the example application in the bug report to <2 seconds on my machine.

Hannes Greule has updated the pull request incrementally with one additional commit since the last revision:

  reword -> initial klass

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Changes:
  - all: https://git.openjdk.org/jdk/pull/16083/files
  - new: https://git.openjdk.org/jdk/pull/16083/files/26f5dcdd..f303a227

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16083&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16083&range=02-03

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/16083.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16083/head:pull/16083

PR: https://git.openjdk.org/jdk/pull/16083