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

[Ilarion Nakonechnyy]

Continuation of PR#10

-------------

Commit messages:
 - Merge branch 'crac' into crac-jcmd
 - Rename stream to jcmd as the only possible
 - Fix another whitespace problem
 - fixup! Fix style a bit
 - Print whole exception to jcmd, as for API
 - fixup! Refactor a bit around linux attach
 - Fix assert on checkpointRestore API call
 - fixup! Fix style a bit
 - Refactor a bit around linux attach op
 - Fix style a bit
 - ... and 40 more: https://git.openjdk.org/crac/compare/217d5bc6...f11cd65a

Changes: https://git.openjdk.org/crac/pull/33/files
 Webrev: https://webrevs.openjdk.org/?repo=crac&pr=33&range=00
  Stats: 411 lines in 11 files changed: 257 ins; 96 del; 58 mod
  Patch: https://git.openjdk.org/crac/pull/33.diff
  Fetch: git fetch https://git.openjdk.org/crac pull/33/head:pull/33

PR: https://git.openjdk.org/crac/pull/33