[lworld+fp16] RFR: 8345053: Add support for FP16 valueOf routines

[Bhavana Kilambi]

This patch adds mid-end support for Float16.valueOf() routines - conversions from int/long/double to half float and backend aarch64 support.

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Commit messages:
 - 8345053: Add support for FP16 valueOf routines

Changes: https://git.openjdk.org/valhalla/pull/1332/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1332&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8345053
  Stats: 1308 lines in 27 files changed: 609 ins; 2 del; 697 mod
  Patch: https://git.openjdk.org/valhalla/pull/1332.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1332/head:pull/1332

PR: https://git.openjdk.org/valhalla/pull/1332