RFR: Upstream merge to jdk-12+14

[Roman Kennke]

Now that jdk/jdk is stable again, let's merge it, up to tage jdk-12+14.
It brings a lot of goodies:

- 8210829: Modularize allocations in C2
- 8210879: ClassLoaderStatsClosure does raw oop comparison
- 8210857: Allow retiring TLABs and collecting statistics in parallel
- 8210752: Remaining explicit barriers for C2
- 8132849: Increased stop time in cleanup phase because of
single-threaded walk of thread stacks in
NMethodSweeper::mark_active_nmethods()
- 8210885: Convert left over loads/stores to access api
- 8211269: Make declaration of Allocation protected in MemAllocator
- 8211241: Missing obj equals in TemplateTable::fast_aldc
- 8211231: BarrierSetC1::generate_referent_check() confuses register
allocator
- 8210887: Tweak C2 gc api for arraycopy
- 8211384: Obsolete -XX:+/-MonitorInUseLists option

Most of it reduces our upstream-diff. We shall pick up parallel TLAB
retiring soon.

http://cr.openjdk.java.net/~rkennke/upstream-jdk12-merge-2018-10-04/outgoing.txt

Testing: tier3_gc_shenandoah ok

Ok to push?