RFR: 8252842: Extend jmap to support parallel heap dump [v33]

[Lin Zang]

> 8252842: Extend jmap to support parallel heap dump

Lin Zang has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 49 commits:

 - fix parallel issue
 - Merge branch 'master' into pd-fix
 - Merge branch 'master' of https://github.com/openjdk/jdk
 - fix build error
 - rewrite dumper and writer number calculation logic
 - Merge branch 'master' into par-dump
 - Merge branch 'master' of https://github.com/openjdk/jdk
 - remove gzipaccessor
 - fix build error
 - Merge branch 'master' into par-dump
 - ... and 39 more: https://git.openjdk.java.net/jdk/compare/fe89dd3b...26255e3f

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Changes: https://git.openjdk.java.net/jdk/pull/2261/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2261&range=32
  Stats: 848 lines in 6 files changed: 653 ins; 42 del; 153 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2261.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2261/head:pull/2261

PR: https://git.openjdk.java.net/jdk/pull/2261