[vectorIntrinsics+fp16] RFR: 8290204: FP16 initial backend implementation [v3]

[Smita Kamath]

> Initial backend implementation for enabling FP16.

Smita Kamath has updated the pull request incrementally with one additional commit since the last revision:

  Addressed review comments

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Changes:
  - all: https://git.openjdk.org/panama-vector/pull/204/files
  - new: https://git.openjdk.org/panama-vector/pull/204/files/90ff380c..6cb10daf

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=panama-vector&pr=204&range=02
 - incr: https://webrevs.openjdk.org/?repo=panama-vector&pr=204&range=01-02

  Stats: 95 lines in 6 files changed: 35 ins; 52 del; 8 mod
  Patch: https://git.openjdk.org/panama-vector/pull/204.diff
  Fetch: git fetch https://git.openjdk.org/panama-vector pull/204/head:pull/204

PR: https://git.openjdk.org/panama-vector/pull/204