RFR: 8259948: Aarch64: Add cast nodes for Aarch64 Neon backend [v6]

[Wang Huang]

> * In this issue, we plan to complete all missing implementation for aarch64 neon backend. For example, cast from Byte to Long, cast from Long to Byte, and so on.
> * It may be a solver of JDK-8269866, or part of it.

Wang Huang has updated the pull request incrementally with one additional commit since the last revision:

  code refine

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4839/files
  - new: https://git.openjdk.java.net/jdk/pull/4839/files/4f0613cb..2fca8cd3

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4839&range=05
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4839&range=04-05

  Stats: 23 lines in 6 files changed: 1 ins; 4 del; 18 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4839.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4839/head:pull/4839

PR: https://git.openjdk.java.net/jdk/pull/4839