RFR (S) 8242229: Shenandoah: inline ShenandoahHeapRegion liveness-related methods

[Aleksey Shipilev]

RFE:
  https://bugs.openjdk.java.net/browse/JDK-8242229

Webrev:
  https://cr.openjdk.java.net/~shade/8242229/webrev.01/

These methods are used on critical paths during choosing the collection set, and should be inlined.

While shenandoahHeapRegion.inline.hpp is transitively included by shenandoahHeap.inline.hpp, which
pretty much every other compilation unit includes, I still opted to include it directly in the
affected compilation units.

Testing: hotspot_gc_shenadoah, benchmarks, eyeballing disassemblies, non-PCH {slowdebug,
fastdebug,release} builds

-- 
Thanks,
-Aleksey