[crac] RFR: Report checkpoint processing to jcmd [v2]

[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 one additional commit since the last revision:

  Rework closing the jcmd socket.
  New approach, a bit complicated but proper -
  save an AttachOperation ( from jcmd )
  and call "complete()"  as attach operation function.

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Changes:
  - all: https://git.openjdk.org/crac/pull/10/files
  - new: https://git.openjdk.org/crac/pull/10/files/3350d505..bb3f6b19

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=crac&pr=10&range=01
 - incr: https://webrevs.openjdk.org/?repo=crac&pr=10&range=00-01

  Stats: 42 lines in 4 files changed: 30 ins; 7 del; 5 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