[crac] RFR: 8375044: [CRaC] Structured engine options info

[Radim Vansa]

Currently the engine documents all exposed options through the description extension; this has some downsides:

* when the JVM wants to change engine option default, -XX:CRaCEngineOptions=help would print wrong value
* options completely controlled by JVM (such as image_location) are reported, too
* options documentation format is fully up to the engine (and it would be more complicated to reflow lines in the output)

The solution is exposing options info in a more structured manner.

As an extra feature we can use -XX:CRaCEngineOptions=help=foo to limit help to only those containing 'foo' in the name.

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Commit messages:
 - 8375044: [CRaC] Structured engine options info

Changes: https://git.openjdk.org/crac/pull/286/files
  Webrev: https://webrevs.openjdk.org/?repo=crac&pr=286&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8375044
  Stats: 195 lines in 7 files changed: 128 ins; 24 del; 43 mod
  Patch: https://git.openjdk.org/crac/pull/286.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/286/head:pull/286

PR: https://git.openjdk.org/crac/pull/286