RFR (S) 8241748: Shenandoah: inline MarkingContext TAMS methods

[Roman Kennke]

ok!

Thanks,
Roman

> RFE:
>   https://bugs.openjdk.java.net/browse/JDK-8241748
> 
> ShenandoahMarkingContext methods that deal with TAMS are accessed on hot paths. These should be inlined.
> 
> Webrev:
>   https://cr.openjdk.java.net/~shade/8241748/webrev.01/
> 
> Testing: hotspot_gc_shenandoah; Linux x86_64 {slowdebug, fastdebug, release} builds without PCH
>