[lworld] RFR: 8335483: [lworld] identity class extending Number should not get the new serialization related warning

[Vicente Romero]

no serialization warning for identity classes extending Number

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Commit messages:
 - 8335483: [lworld] identity class extending Number should not get the new serialization related warning

Changes: https://git.openjdk.org/valhalla/pull/1153/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1153&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8335483
  Stats: 22 lines in 3 files changed: 19 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/valhalla/pull/1153.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1153/head:pull/1153

PR: https://git.openjdk.org/valhalla/pull/1153