RFR: Wipe out ShenandoahStoreCheck implementation

[Roman Kennke]

Hi Aleksey,

that's great. Let's wipe it out.

Thanks, Roman

> Our experimental ShenandoahStoreCheck implementation has been with us for about two years, and we
> have never seen it fail. It makes little benefit to keep it on many paths in shared code, especially
> in .ad files. It is not complete as well: there are paths not covered by this thing, and completing
> it would balloon up our upstream exposure.
> 
> We also have the idea to reimplement this with optional aliased heap [1], which would hopefully be
> less intrusive. For that, we keep the flag around.
> 
> This patch wipes out ShenandoahStoreCheck implementation:
>   http://cr.openjdk.java.net/~shade/shenandoah/store-check-wipe/webrev.01/
> 
> Testing: x86_64 and aarch64 builds, x86_64 hotspot_fast_gc_shenandoah
> 
> Thanks,
> -Aleksey
> 
> [1] http://mail.openjdk.java.net/pipermail/shenandoah-dev/2018-January/004816.html
>