[vectorIntrinsics+compress] RFR: 8274837: Intel backend support for compress VectorAPI

[Joshua Zhu]

I separate my implementation of "compress" API into several patches for easy review.
This patch is the change in backend used to support vector-to-vector compress API.
ByteVector and ShortVector are supported in AVX512vbmi2.

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Commit messages:
 - 8274837: Intel backend support for compress VectorAPI

Changes: https://git.openjdk.java.net/panama-vector/pull/144/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=144&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274837
  Stats: 136 lines in 9 files changed: 134 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/144.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/144/head:pull/144

PR: https://git.openjdk.java.net/panama-vector/pull/144