RFR: 8296785: Use realloc for CHeap-allocated BitMaps [v2]

[Stefan Karlsson]

> Today CHeap allocated bitmaps don't resize with realloc. I'd like to change that by fixing that by adding support for realloc in the ArrayAllocator classes, and then use that when resizing the bitmaps.
> 
> We've been using and testing one version of this patch in the Generational ZGC repository for a while now. That version is slightly different because of recent rewrites of the bitmaps, but in essence the same. See:
> https://github.com/openjdk/zgc/commit/ca692f686bda8d86d3786c2afc782bfdc54fbdfc

Stefan Karlsson has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - 8296785: Use realloc for CHeap-allocated BitMaps
 - Merge remote-tracking branch 'upstream/master' into 8296774_bitmap_stricter_construction
 - 8296774: Removed default MEMFLAGS value from CHeapBitMap

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Changes:
  - all: https://git.openjdk.org/jdk/pull/11102/files
  - new: https://git.openjdk.org/jdk/pull/11102/files/f13888b8..f13888b8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11102&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11102&range=00-01

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/11102.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11102/head:pull/11102

PR: https://git.openjdk.org/jdk/pull/11102