[lworld] RFR: 8288131: [lworld] Implement javac flag -XDenablePrimitiveClasses [v6]

[Vicente Romero]

> Primitive classes support should be opted in using a compiler option

Vicente Romero has updated the pull request incrementally with one additional commit since the last revision:

  VarHandles tests

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Changes:
  - all: https://git.openjdk.org/valhalla/pull/758/files
  - new: https://git.openjdk.org/valhalla/pull/758/files/e42cd658..39363cca

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=758&range=05
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=758&range=04-05

  Stats: 32 lines in 32 files changed: 32 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/valhalla/pull/758.diff
  Fetch: git fetch https://git.openjdk.org/valhalla pull/758/head:pull/758

PR: https://git.openjdk.org/valhalla/pull/758