RFR: 8296139: Make GrowableBitMap the base class of all implementations [v4]

[Xin Liu]

> BitMap is an abstract class. All subclasses provide their own allocators. It is the allocator brings the capability to 'resize' the container. 
> I would like to add a new 'GrowableBitmap' and make it the common base class. 
> 
> To substitute 'VectorSet', we also need to merge ResourceBitMap and ArenaBitMap because VectorSet supports Resource and Arena storage at the same time. 
> This patch unifies them.  ResourceBitMap is a specialized ArenaBitMap whose allocator is with NULL arena.
> 
> All subclasses of GrowableBitMap are elastic. I will add new interface like VectorSet::test_set(index). It will grow to include the new index.

Xin Liu has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains eight commits:

 - Merge branch 'master' into JDK-8296139
 - Bring back verify_size to the constructor of BitMap.
   
   Also resume the underlying member data to be private. Subclasses of
   GrowableBitMap update them using update(map, size).
 - Reivew comments from stefank
 - Refactor GrowableBitMap using C++ CRTP
   
   With CPTP, we don't need to have explicit Allocators. Subclasses expose
   allocate/free member functions upward to GrowableBitMap<BitMapWithAllocator>. This
   aproach is similar to GrowableArray.
 - Add unittest for Arena.
 - Avoid polluting namespace.
   
   uses qualified bm_word_t and idx_t.
 - Change ResourceBitMap to subclass of ArenaBitMap.
 - Add GrowableBitMap.

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Changes: https://git.openjdk.org/jdk/pull/10941/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10941&range=03
  Stats: 280 lines in 3 files changed: 85 ins; 143 del; 52 mod
  Patch: https://git.openjdk.org/jdk/pull/10941.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10941/head:pull/10941

PR: https://git.openjdk.org/jdk/pull/10941