[vectorIntrinsics+mask] RFR: 8265109: SVE predicate register allocation support for vectorIntrinsics

[Ningsheng Jian]

This is the SVE predicate register allocation part for Vector API masking support. Since we don't have sufficent usages to test it in
jdk/jdk, and based on @sviswa7 's proposal [1], we would like to put it to vectorIntrinsics+mask first and get tested here with further predicate-based vector masking support, though so far no issue found with Xiaohong's initial Vector API masking support.

[1] https://mail.openjdk.java.net/pipermail/panama-dev/2021-April/012920.html

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

Commit messages:
 - 8265109: SVE predicate register allocation support for vectorIntrinsics

Changes: https://git.openjdk.java.net/panama-vector/pull/65/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=65&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8265109
  Stats: 314 lines in 17 files changed: 265 ins; 5 del; 44 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/65.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/65/head:pull/65

PR: https://git.openjdk.java.net/panama-vector/pull/65