[lworld+fp16] RFR: 8339494: Porting HalfFloatVector classes.

[Jatin Bhateja]

- Port existing HalfFloatVector and its concrete vector classes from vectorIntrinsics+fp16 to lworld+fp16.
- These new vector classes uses Float16 array as their backing storage.
- Idea is to enable intrinsificaiton of new HalfFloatVector operations and leverage existing Float16 auto-vectorization and backend support.

All existing VectorAPI tests are passing with the patch.

Best Regards,
Jatin

Follow up work:-
a) Jtreg suite extensions to cover HalfFloatVector operations.
b) Handle Float16 lane type in vector API inline expansion layer.

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Commit messages:
 - 8339494: Porting HalfFloatVector classes.

Changes: https://git.openjdk.org/valhalla/pull/1233/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1233&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339494
  Stats: 9455 lines in 58 files changed: 8786 ins; 17 del; 652 mod
  Patch: https://git.openjdk.org/valhalla/pull/1233.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1233/head:pull/1233

PR: https://git.openjdk.org/valhalla/pull/1233