RFR: 8341260: Add Float16 to jdk.incubator.vector [v15]

[Joe Darcy]

> Port of Float16 from java.lang in the lworld+fp16 branch to jdk.incubabor.vector.

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

  Cleanup pass on tests.

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/21574/files
  - new: https://git.openjdk.org/jdk/pull/21574/files/5ed21469..d39575f0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21574&range=14
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21574&range=13-14

  Stats: 80 lines in 1 file changed: 7 ins; 20 del; 53 mod
  Patch: https://git.openjdk.org/jdk/pull/21574.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21574/head:pull/21574

PR: https://git.openjdk.org/jdk/pull/21574