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

[Radim Vansa]

On Mon, 30 Jun 2025 17:21:50 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

src/java.base/linux/native/pauseengine/pauseengine.c line 68:

> 66:         fclose(pidfile);
> 67: 
> 68:         printf(PAUSEENGINE "pausing the process, restore in another process to unpause it\n");

I would rather see all these logging messages going into `stderr`.

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PR Review Comment: https://git.openjdk.org/crac/pull/239#discussion_r2176883220