[lworld+fp16] RFR: 8339473: Add support for FP16 isFinite, isInfinite and isNaN [v4]

[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 incrementally with one additional commit since the last revision:

  Add more regression tests for FP16 isFinite, isInfinite, isNaN

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Changes:
  - all: https://git.openjdk.org/valhalla/pull/1239/files
  - new: https://git.openjdk.org/valhalla/pull/1239/files/a116fbe8..e965b58c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=1239&range=03
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=1239&range=02-03

  Stats: 131 lines in 2 files changed: 48 ins; 8 del; 75 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