RFR: 8263421: Module image file is opened twice during VM startup

[Harold Seigel]

Please review this fix for JDK-8263421.  The fix stores the JImageFile* in a static that gets initialized when lookup_vm_options() opens the module image file.  The static JimageFIle* is then used by setup_bootstrap_search_path_impl() when creating the ClassPathImageEntry for the module image file, avoiding having to re-open the module image file.

This fix moved the creation of the ClassPathImageEntry for the module image file from create_class_path_entry() to setup_bootstrap_search_path_impl() because create_class_path_entry() may try to do this multiple times, but the ClassPathImageEntry for the module image file is only actually created once.

The fix also removes some unused code related to module image file processing.

The changes were tested with Mach5 tiers 1 and 2 on Linux, Mac OS, and Windows, and Mach5 tiers 3-
5 on Linux x64.

Thanks, Harold

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Commit messages:
 - 8263421: Module image file is opened twice during VM startup

Changes: https://git.openjdk.java.net/jdk/pull/3591/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3591&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263421
  Stats: 61 lines in 2 files changed: 17 ins; 21 del; 23 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3591.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3591/head:pull/3591

PR: https://git.openjdk.java.net/jdk/pull/3591