RFR: Merge lworld [v2]

[David Simms]

> Merge tag 'jdk-16+19'
> 
> Merge branch 'lworld' into type-restrictions_merge_16_19

David Simms has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev
excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since
the last revision:

 - Merge branch 'lworld' into type-restrictions_merge_16_19
 - 8254022: [lworld] [type-restrictions] Initial support for RestrictedField
   
   Reviewed-by: dsimms
 - 8253760: [type-restrictions] Static inline fields are not "erased" to the ref type
 - 8253312: Enable JVM experiments in specialization under an opt-in mode

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

Changes:
  - all: https://git.openjdk.java.net/valhalla/pull/217/files
  - new: https://git.openjdk.java.net/valhalla/pull/217/files/d0d81c2d..d0d81c2d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=valhalla&pr=217&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=valhalla&pr=217&range=00-01

  Stats: 0 lines in 0 files changed: 0 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/217.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/217/head:pull/217

PR: https://git.openjdk.java.net/valhalla/pull/217