RFR: 8325471: CHeapBitMap(MEMFLAGS flags) constructor misleading use of super-constructor

[Axel Boldt-Christmas]

The `explicit CHeapBitMap(MEMFLAGS flags)` calls the `GrowableBitMap(bm_word_t* map, idx_t size_in_bits)` super-constructor with `GrowableBitMap(0, false)`. This works because `0` gets converted to `nullptr` and `false` gets converted to `0`. However this seems to have be a miss in the most recent refactoring and is misleading.

`explicit CHeapBitMap(MEMFLAGS flags)` should use `GrowableBitMap()` directly which creates an empty (uninitialised) bitmap.

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Commit messages:
 - 8325471: CHeapBitMap(MEMFLAGS flags) constructor misleading use of super-constructor

Changes: https://git.openjdk.org/jdk/pull/17768/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17768&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8325471
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/17768.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17768/head:pull/17768

PR: https://git.openjdk.org/jdk/pull/17768