RFR: 8254274: Development to add 'lint' warning for @ValueBased classes

[Srikanth Adayapalam]

New javac lint mode (-Xlint:synchronize) to warn about client side as well JDK internal attempts to synchronize on instances of value based classes

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Commit messages:
 - 8254274: Lint mode to warn on synchronization attempts on instances of value based classes

Changes: https://git.openjdk.java.net/valhalla/pull/237/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=237&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8254274
  Stats: 352 lines in 20 files changed: 352 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/237.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/237/head:pull/237

PR: https://git.openjdk.java.net/valhalla/pull/237