[crac] RFR: 8361124: [CRaC] Move recursive checkpoint test to simengine

[Radim Vansa]

On Tue, 1 Jul 2025 07:18:51 GMT, Timofei Pushkin <tpushkin at openjdk.org> wrote:

> At the moment of creation this PR includes #239 — that should be merged first. fc33e85c429536dcc89ff59afed6450bb7562639 is the change of this PR.
> 
> Makes recursive checkpoint test use `simengine` instead of `pauseengine`. Since that was the only test using `pauseengine`, a separate `PauseEngineTest` is created to test the engine.

I don't really like `RecursiveCheckpointTest.exception` being not synchronized at all; could you turn this into a concurrent collection?

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PR Review: https://git.openjdk.org/crac/pull/240#pullrequestreview-2974464402