[crac] RFR: 8361090: [CRaC] Make dev engines less confusing [v2]

[Radim Vansa]

On Tue, 1 Jul 2025 12:56:56 GMT, Timofei Pushkin <tpushkin at openjdk.org> wrote:

>> - Makes `pauseengine` Linux-only since it is not fully implemented on MacOS and Windows
>>    - Also moves `criuengine` sources from `unix` to `linux` directory since it only supports Linux anyway
>> - Makes `simengine` and `pausengine` report errors and status in more details
>
> Timofei Pushkin has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Log to stderr

Marked as reviewed by rvansa (Committer).

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PR Review: https://git.openjdk.org/crac/pull/239#pullrequestreview-2978492569