[vectorIntrinsics+compress] RFR: 8274839: Intrinsic support for compress & expand VectorAPI

[Joshua Zhu]

I separate my implementation of "compress" API into several patches for easy review.
This change is the intrinsic support for compress/expand API.
The intrinsic method "selectiveOp" in VectorSupport accepts boolean to indicate expansion or compression.

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Commit messages:
 - 8274839: Intrinsic support for compress & expand VectorAPI

Changes: https://git.openjdk.java.net/panama-vector/pull/145/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=145&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274839
  Stats: 146 lines in 7 files changed: 145 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/145.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/145/head:pull/145

PR: https://git.openjdk.java.net/panama-vector/pull/145