[lworld] RFR: 8288131: [lworld] Implement javac flag -XDenablePrimitiveClasses [v4]

[Vicente Romero]

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

Vicente Romero has updated the pull request incrementally with two additional commits since the last revision:

 - fixing varhandle tests
 - fixing benchmark tests

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/758/files
  - new: https://git.openjdk.org/valhalla/pull/758/files/e532288d..bc67d2c9

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=758&range=03
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=758&range=02-03

  Stats: 333 lines in 34 files changed: 254 ins; 4 del; 75 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