RFR: 8345125: Aarch64: Add aarch64 backend for Float16 operations

[Bhavana Kilambi]

This patch adds aarch64 backend for scalar FP16 operations namely - add, subtract, multiply, divide, fma, sqrt, min and max.

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Commit messages:
 - 8345125: Aarch64: Add aarch64 backend for Float16 operations

Changes: https://git.openjdk.org/jdk/pull/23748/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23748&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8345125
  Stats: 1007 lines in 13 files changed: 326 ins; 1 del; 680 mod
  Patch: https://git.openjdk.org/jdk/pull/23748.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23748/head:pull/23748

PR: https://git.openjdk.org/jdk/pull/23748