RFR: 8355585: Aarch64: Add aarch64 backend for Float16 vector operations [v3]

[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:

  Remove additional spaces in the aarch64_vector_ad.m4 file

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Changes:
  - all: https://git.openjdk.org/jdk/pull/25096/files
  - new: https://git.openjdk.org/jdk/pull/25096/files/080a0ce8..31103f69

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=25096&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=25096&range=01-02

  Stats: 26 lines in 2 files changed: 0 ins; 0 del; 26 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