RFR: 8355585: Aarch64: Add aarch64 backend for Float16 vector operations [v2]

[Bhavana Kilambi]

> This patch adds aarch64 backend (both Neon and SVE) for FP16 vector operations - add, mul, sub, div, min, max, sqrt and fma.
> 
> Testing:
> JTREG tests - hotspot_all, jdk (tier 1-3) and langtools (tier 1) pass on aarch64 which also includes the JTREG test to test the FP16 vector operations - `test/hotspot/jtreg/compiler/vectorization/TestFloat16VectorOperations.java`

Bhavana Kilambi has updated the pull request incrementally with one additional commit since the last revision:

  Address review comments

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/25096/files
  - new: https://git.openjdk.org/jdk/pull/25096/files/56edd6df..080a0ce8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25096&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25096&range=00-01

  Stats: 123 lines in 3 files changed: 26 ins; 95 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/25096.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25096/head:pull/25096

PR: https://git.openjdk.org/jdk/pull/25096