RFR: 8315431: ArchiveHeapWriter::get_filler_size_at() cannot handle buffer expansion [v2]

[Ioi Lam]

> In `ArchiveHeapWriter::maybe_fill_gc_region_gap()`:
> 
> - The address of `filler` will change if the buffer (which is a GrowableArrayCHeap) expands.
> - Instead of storing the address, we store the offset of `filler` from the beginning of the buffer. This offset will not change even if the buffer expands.

Ioi Lam 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 two additional commits since the last revision:

 - Merge branch 'master' into 8315431-filler-size-at-cannot-handle-buffer-expansion
 - 8315431: ArchiveHeapWriter::get_filler_size_at() cannot handle buffer expansion

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/18920/files
  - new: https://git.openjdk.org/jdk/pull/18920/files/9f79b25b..81315b0b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18920&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18920&range=00-01

  Stats: 51101 lines in 2118 files changed: 23649 ins; 18336 del; 9116 mod
  Patch: https://git.openjdk.org/jdk/pull/18920.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18920/head:pull/18920

PR: https://git.openjdk.org/jdk/pull/18920