RFR: 8269478: Shenandoah: gc/shenandoah/mxbeans tests should fail when no notifications arrive [v3]

[Aleksey Shipilev]

On Mon, 28 Jun 2021 16:43:42 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> After JDK-8259954, some mxbeans tests wait in the effectively infinite loop for the notifications to arrive. If notifications are broken, it would wait forever, and test would timeout. We need to make such failure mode more straightforward.
>> 
>> Additional testing: 
>>  - [x] Linux x86_64 fastdebug `gc/shenandoah/mxbeans` 
>>  - [x] Linux x86_64 fastdebug `gc/shenandoah/mxbeans`, `-Xcomp`
>
> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Rework tests for much better reliability, passes slowdebug+Xcomp

I have rewritten the tests so that they pass `slowdebug` + `-Xcomp`. Also they are looking at the actual timeout configuration for the test, so users can control how long to wait with usual `timeoutFactor`.

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PR: https://git.openjdk.java.net/jdk/pull/4611