[vectorIntrinsics+mask] RFR: 8268154: Add masking support for vector load intrinsics [v2]

[Xiaohong Gong]

> This patch adds the predicate support for masked load vector operation, including the Vector API java implementation and hotspot intrinsics changes. The main changes contain:
>   - Adding a new hotspot intrinsic method (`loadMasked`), which can transform the vector mask class and value to hotspot. It is called by the masked `"fromArray"` API in JAVA level. The compiler will generate the masked vector load node if the current platform supports the predicate feature and backend has implemented it. Otherwise, the vector blend pattern will be generated like before.
>   - Adding the similar masked support for load/store boolean/char array.
> 
> Note that the intrinsification when there is the array range bailout is not implemented in this patch. We are considering making it vectorized with predicate feature for SVE/AVX-512 as well, and will create a separate patch for it in future.
> 
> Also note that this patch doesn't contain any backend changes.

Xiaohong Gong has updated the pull request incrementally with one additional commit since the last revision:

  Address review comments

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Changes:
  - all: https://git.openjdk.java.net/panama-vector/pull/90/files
  - new: https://git.openjdk.java.net/panama-vector/pull/90/files/106585f6..0b77c8e3

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=90&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=90&range=00-01

  Stats: 62 lines in 9 files changed: 24 ins; 10 del; 28 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/90.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/90/head:pull/90

PR: https://git.openjdk.java.net/panama-vector/pull/90