RFR: 8287771: Remove useless G1 After GC summary refinement and sampling thread times [v4]

[tqxia]

On Thu, 16 Jun 2022 00:27:55 GMT, tqxia <duke at openjdk.org> wrote:

>> In the "After GC summary" printed by gc+remset=trace and G1RemsetStatsSummaryPeriod > 1 we print refinement and sampling thread times. However during GC neither thread types are active, so it always prints zeros.
>> 
>> Remove the printing of these unnecessary values in the after gc summary.
>
> tqxia has updated the pull request incrementally with one additional commit since the last revision:
> 
>   add comment

Thanks for the review!

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PR: https://git.openjdk.org/jdk/pull/9106