[crac] RFR: Report checkpoint processing to jcmd [v5]

[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 four additional commits since the last revision:

 - reworked socket fd validation -
   get an fd from linuxAttach operation
 - addressing review notes 2
 - address review notes
 - corrections

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Changes:
  - all: https://git.openjdk.org/crac/pull/10/files
  - new: https://git.openjdk.org/crac/pull/10/files/3d9b0f70..b890d28e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=crac&pr=10&range=04
 - incr: https://webrevs.openjdk.org/?repo=crac&pr=10&range=03-04

  Stats: 290 lines in 7 files changed: 59 ins; 197 del; 34 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