RFR: Restore ShenandoahVerify functionality for generational mode [v2]

[earthling-amzn]

On Thu, 18 Mar 2021 16:38:53 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> earthling-amzn has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Place '*' next to type, not variable
>>   
>>   Also remove unapproved 'override' keyword
>
> Very nice! Looks good except a few stylistic nits.
> How far away is it from running all of hotspot_gc_shenandoah with added generational runners?

@rkennke - to answer your question about testing. The generational mode has failures if the test causes a FullGC to run (this is expected right now). It also looks like there may be an issue with `UseStringDeduplication`, but we haven't investigated this yet. Apart from those failures we pass ~200 out of 234 hotspot_gc_shenandoah tests.

-------------

PR: https://git.openjdk.java.net/shenandoah/pull/24