RFR: [type-classes] 8376250: Upgrade Bfloat16 to use operators [v2]

[Joe Darcy]

> Update Bfloat16 to use operators; small adjustment to StandardFloatingPoint

Joe Darcy has updated the pull request incrementally with one additional commit since the last revision:

  Improve comments in test.

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Changes:
  - all: https://git.openjdk.org/valhalla/pull/1958/files
  - new: https://git.openjdk.org/valhalla/pull/1958/files/434fdd66..38681078

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1958&range=01
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1958&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 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