[crac] RFR: Report checkpoint processing to jcmd [v22]

[Ilarion Nakonechnyy]

> pass output stream from diagnosticCommand.cpp through java code into os_linux.cpp::VM_crac::doit()

Ilarion Nakonechnyy has updated the pull request incrementally with two additional commits since the last revision:

 - review notes address
 - style corrections

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Changes:
  - all: https://git.openjdk.org/crac/pull/10/files
  - new: https://git.openjdk.org/crac/pull/10/files/c58902f3..ba53bdb6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=crac&pr=10&range=21
 - incr: https://webrevs.openjdk.org/?repo=crac&pr=10&range=20-21

  Stats: 82 lines in 10 files changed: 10 ins; 5 del; 67 mod
  Patch: https://git.openjdk.org/crac/pull/10.diff
  Fetch: git fetch https://git.openjdk.org/crac pull/10/head:pull/10

PR: https://git.openjdk.org/crac/pull/10