RFR: 8255125: [Development] copy jdk.internal.ValueBased to jep390 branch

[Roger Riggs]

Commit a copy of the ValueBased.java and its uses to the JEP 390 branch.

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Commit messages:
 - 8254797: [Development] Define & apply annotation jdk.internal.ValueBased

Changes: https://git.openjdk.java.net/valhalla/pull/235/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=235&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255125
  Stats: 80 lines in 37 files changed: 78 ins; 1 del; 1 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/235.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/235/head:pull/235

PR: https://git.openjdk.java.net/valhalla/pull/235