[lworld] RFR: 8366093: [lworld] Add preview mode to C++ classloader [v3]

[David Beaumont]

> C++ changes for supporting preview mode when preview mode resources (with new location flags) are available.
> 
> At the moment, this code will operate on non-preview jimage files (1.0) and act as if no preview resources are available by virtue of the default value for missing attributes being zero (which matches location flags for "normal" entries).

David Beaumont has updated the pull request incrementally with one additional commit since the last revision:

  feedback tweaks

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/1618/files
  - new: https://git.openjdk.org/valhalla/pull/1618/files/2b805fb0..7c28f220

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1618&range=02
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1618&range=01-02

  Stats: 5 lines in 2 files changed: 2 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/valhalla/pull/1618.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1618/head:pull/1618

PR: https://git.openjdk.org/valhalla/pull/1618