RFR: 8311175: Move BufWriter::asByteBuffer to BufWriterImpl [v2]

[Chen Liang]

> As discussed on the mailing list https://mail.openjdk.org/pipermail/classfile-api-dev/2023-June/000381.html, BufWriter::asByteBuffer has a behavior not suitable for API and is only used by internal StackMapGenerator/StackCounter, so it will be converted to an internal API.
> 
> Somehow the ByteBuffer needs to be sliced, or StackMapGenerator encounters IOOBE. Not sure what the exact cause was.

Chen Liang 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' of https://github.com/openjdk/jdk into fix/asbb-internal
 - Convert asByteBuffer to an internal API

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/14736/files
  - new: https://git.openjdk.org/jdk/pull/14736/files/5c25188c..d82789c3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14736&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14736&range=00-01

  Stats: 1808836 lines in 17143 files changed: 485717 ins; 823338 del; 499781 mod
  Patch: https://git.openjdk.org/jdk/pull/14736.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14736/head:pull/14736

PR: https://git.openjdk.org/jdk/pull/14736