RFR: 8376250: Upgrade Bfloat16 to use operators

[Joe Darcy]

Update Bfloat16 to use operators; small adjustment to StandardFloatingPoint

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Commit messages:
 - Refine StandardFloatingPoint; upgrade Bfloat16 for operators.
 - Merge branch 'type-classes' into JDK-8376250
 - JDK-8376250: Upgrade Bfloat16 to use operators

Changes: https://git.openjdk.org/valhalla/pull/1958/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1958&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8376250
  Stats: 205 lines in 5 files changed: 199 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/valhalla/pull/1958.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1958/head:pull/1958

PR: https://git.openjdk.org/valhalla/pull/1958