[14] RFR 8242301: Shenandoah: Inline LRB runtime call

[Aleksey Shipilev]

Original RFE:
  https://bugs.openjdk.java.net/browse/JDK-8242301
  https://hg.openjdk.java.net/jdk/jdk/rev/9a001fab4846

Some context mismatches in 14u, here's the webrev:
  https://cr.openjdk.java.net/~shade/8242301/webrev.14u.01/

Testing: hotspot_gc_shenandoah {fastdebug,release}

-- 
Thanks,
-Aleksey