Merge

8146399: Refactor the BlockOffsetTable classes.
Reviewed-by: mgerdin, jwilhelm, tschatzl

Merge

8134994: use separate VMStructs databases for SA and JVMCI
Reviewed-by: kbarrett

8144996: Replace the HeapRegionSetCount class with an uint
Reviewed-by: brutisso, jwilhelm

8143014: Access PtrQueue member offsets through derived classes
Summary: Moved accessors to derived classes and updated callers.
Reviewed-by: tschatzl, jmasa, twisti

8067336: Allow that PLAB allocations at the end of regions are flexible
Summary: PLAB allocations may return a buffer that is between minimum size (current allocation) and the desired size. This allows removes a large amount of fragmentation at the end of regions.
Reviewed-by: tbenson, mgerdin

8131319: Move G1Allocator::_summary_bytes_used back to G1CollectedHeap
Summary: G1Allocator::_summary_bytes_used fits better in G1CollectedHeap since we added the archive allocator. Move it back to the original location.
Reviewed-by: mgerdin, tbenson

8079792: GC directory structure cleanup
Reviewed-by: brutisso, stefank, david