[crac] RFR: 8376959: [CRaC] Turn simengine into shared library

[Radim Vansa]

Right now `simengine` is implemented as an executable, invoked through `libcrexec` that implements the C/R API. Since the programmatic C/R API should be the main interface, any exec API is redundant; let's turn `simengine` into shared (dynamic) library implementing the API on its own.

The `pauseengine` does not need to exist on its own; this can be only an option `pause=true` for `simengine`. The implementation is Linux only (and it is out of scope to fill in a non-Linux implementation - the `pause` option can be just excluded in non-Linux `libsimengine`).

We expect to turn `libcrexec` + `criuengine` into `libcriuengine` in a follow up (not as part of this issue).

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Commit messages:
 - JDK-8376959: [CRaC] Turn simengine into shared library

Changes: https://git.openjdk.org/crac/pull/289/files
  Webrev: https://webrevs.openjdk.org/?repo=crac&pr=289&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8376959
  Stats: 2810 lines in 26 files changed: 1602 ins; 1145 del; 63 mod
  Patch: https://git.openjdk.org/crac/pull/289.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/289/head:pull/289

PR: https://git.openjdk.org/crac/pull/289