[code-reflection] Integrated: Move certain classes into non-exportable packages

[Paul Sandoz]

Move certain classes in the bytecode package to a non-exportable packages.

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Commit messages:
 - Hide certain classes.

Changes: https://git.openjdk.org/babylon/pull/449/files
  Webrev: https://webrevs.openjdk.org/?repo=babylon&pr=449&range=00
  Stats: 39 lines in 7 files changed: 20 ins; 16 del; 3 mod
  Patch: https://git.openjdk.org/babylon/pull/449.diff
  Fetch: git fetch https://git.openjdk.org/babylon.git pull/449/head:pull/449

PR: https://git.openjdk.org/babylon/pull/449