[lworld+fp16] RFR: 8339473: Add support for FP16 isFinite, isInfinite and isNaN [v2]

[Bhavana Kilambi]

> This patch adds intrinsic support for FP16 isNaN, isFinite and isInfinite methods and also adds aarch64 backend for these intrinsics.
> 
> Tested all FP16 related tests successfully on aarch64.

Bhavana Kilambi 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 three additional commits since the last revision:

 - Address review comments
 - Merge branch 'lworld+fp16'
 - 8339473: Add support for FP16 isFinite, isInfinite and isNaN
   
   This patch adds intrinsic support for FP16 isNaN, isFinite and
   isInfinite methods and also adds aarch64 backend for these intrinsics.
   
   Tested all FP16 related tests successfully on aarch64.

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

Changes:
  - all: https://git.openjdk.org/valhalla/pull/1239/files
  - new: https://git.openjdk.org/valhalla/pull/1239/files/1d1dfb33..2f8e22ce

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1239&range=01
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1239&range=00-01

  Stats: 883 lines in 12 files changed: 836 ins; 22 del; 25 mod
  Patch: https://git.openjdk.org/valhalla/pull/1239.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1239/head:pull/1239

PR: https://git.openjdk.org/valhalla/pull/1239