RFR: 8368289: [leyden] Expose AOTCodeEntry::_for_preload in VMStructs

[Aleksey Shipilev]

Similar to [JDK-8366811](https://bugs.openjdk.org/browse/JDK-8366811), we also need this bit to disambiguate A4 and AP4 frames in async-profiler.

Additional testing:
 - [x] Linux x86_64 server fastdebug, `runtime/cds`
 - [x] Ad-hoc async-profiler hacks to access this field

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

Commit messages:
 - Move
 - Fix

Changes: https://git.openjdk.org/leyden/pull/98/files
  Webrev: https://webrevs.openjdk.org/?repo=leyden&pr=98&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8368289
  Stats: 3 lines in 2 files changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/leyden/pull/98.diff
  Fetch: git fetch https://git.openjdk.org/leyden.git pull/98/head:pull/98

PR: https://git.openjdk.org/leyden/pull/98