[crac] RFR: 8378446: [CRaC] Replace libcrexec with libcriuengine

[Radim Vansa]

After [JDK-8376959](https://bugs.openjdk.org/browse/JDK-8376959) the only use of libcrexec is running CRIU; in fact the code already is quite CRIU-dependent. The point of this task is to stop pretending that libcrexec is generic, and move code from criuengine binary (now removed) into libcriuengine implementing the C/R API.

This removes smuggling of some parameters through environment variables and execution of the criuengine. We still require anexecuteable (now called `criuhelper`) to become parent of the restored process, but this has significantly simplified implementation.

Replacement of communication between the restoring and restored process through signals and temporary files is out of scope of this change.

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Commit messages:
 - 8378446: [CRaC] Replace libcrexec with libcriuengine

Changes: https://git.openjdk.org/crac/pull/297/files
  Webrev: https://webrevs.openjdk.org/?repo=crac&pr=297&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8378446
  Stats: 2621 lines in 20 files changed: 1034 ins; 1528 del; 59 mod
  Patch: https://git.openjdk.org/crac/pull/297.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/297/head:pull/297

PR: https://git.openjdk.org/crac/pull/297