RFR: 8296785: Use realloc for CHeap-allocated BitMaps

[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

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Depends on: https://git.openjdk.org/jdk/pull/11084

Commit messages:
 - 8296785: Use realloc for CHeap-allocated BitMaps

Changes: https://git.openjdk.org/jdk/pull/11102/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11102&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296785
  Stats: 227 lines in 5 files changed: 174 ins; 31 del; 22 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