[lworld+fp16] RFR: 8338061: Add support for FP16 unary and ternary operations [v3]

[Bhavana Kilambi]

> This patch adds support for three unary operators - abs, neg and sqrt and a ternary operator - fma for FP16.
> Both scalar and vector mid-end support along with aarch64 backend support are added.
> Tested all FP16 tests successfully on aarch64.

Bhavana Kilambi has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:

 - Merge branch 'lworld+fp16'
 - Address review comments
 - Merge branch 'lworld+fp16'
 - 8338061: Add support for FP16 unary and ternary operations
   
   This patch adds support for three unary operators - abs, neg and sqrt
   and a ternary operator - fma for FP16.
   Both scalar and vector mid-end support along with aarch64 backend
   support are added.
   Tested all FP16 tests successfully on aarch64.

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

Changes: https://git.openjdk.org/valhalla/pull/1211/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1211&range=02
  Stats: 1413 lines in 29 files changed: 645 ins; 5 del; 763 mod
  Patch: https://git.openjdk.org/valhalla/pull/1211.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1211/head:pull/1211

PR: https://git.openjdk.org/valhalla/pull/1211