[vectorIntrinsics+fp16] RFR: 8290204: FP16 initial backend implementation [v2]

[Smita Kamath]

> Initial backend implementation for enabling FP16.

Smita Kamath has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge vectorIntrinsics+fp16
 - Initial fp16 backend implementation

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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/e4183337..90ff380c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=panama-vector&pr=204&range=01
 - incr: https://webrevs.openjdk.org/?repo=panama-vector&pr=204&range=00-01

  Stats: 14102 lines in 29 files changed: 13579 ins; 157 del; 366 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