RFR: Merge lworld [v2]

[David Simms]

> Merge lworld at tag jdk-16+21

David Simms has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains seven commits:

 - Merge branch 'lworld' into type-restrictions_merge_jdk_16_21
 - Merge lworld
   
   Merge jdk-16+20
 - 8254254: [lworld][type-restrictions] Serviceability tests failing missing FIELDINFO_TAG_MASK
   
   Reviewed-by: lfoltan
 - Merge lworld
   
   Merge tag 'jdk-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

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Changes: https://git.openjdk.java.net/valhalla/pull/243/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=243&range=01
  Stats: 813 lines in 37 files changed: 638 ins; 103 del; 72 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/243.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/243/head:pull/243

PR: https://git.openjdk.java.net/valhalla/pull/243