RFR (S) 8241583: Shenandoah: turn heap lock asserts into macros

[Roman Kennke]

Ok.

Thank you,
Roman

> RFE:
>   https://bugs.openjdk.java.net/browse/JDK-8241583
> 
> See rationale in the bug.
> 
> Webrev:
>   https://cr.openjdk.java.net/~shade/8241583/webrev.01/
> 
> Testing: hotspot_gc_shenandoah {fastdebug, release}
>