RFR: 8368985: Small Float16 refactorings [v3]

[Joe Darcy]

> A few more small cleanups to Float16 and its tests.

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

  Respond to review feedback.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27587/files
  - new: https://git.openjdk.org/jdk/pull/27587/files/5a96376e..db0613ed

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27587&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27587&range=01-02

  Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/27587.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27587/head:pull/27587

PR: https://git.openjdk.org/jdk/pull/27587