RFR: 8366255: Remove 'package_to_module' function from imageFile.cpp

[David Beaumont]

Removing the 'package_to_module' function from imageFile.cpp and the associated JNI export.
This code isn't used or referenced from anywhere, and removing it makes adapting the package flags for use with preview mode simpler.

A clone of the Valhalla PR:
https://github.com/openjdk/valhalla/pull/1535

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

Commit messages:
 - copyright
 - remove dead code

Changes: https://git.openjdk.org/jdk/pull/26965/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26965&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8366255
  Stats: 139 lines in 4 files changed: 0 ins; 133 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/26965.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26965/head:pull/26965

PR: https://git.openjdk.org/jdk/pull/26965