[vectorIntrinsics] RFR: 8283598: [vectorapi] Add new vector operation for compress bits

[Smita Kamath]

Hi,

I've added support for new vector operations for compressing bits of integral vector types(Byte/Short/Integer/Long).
The implementation is based on Compress or Generalized Extract mentioned in Hackers Delight by Henry S. Warren, Jr.
The implementation does the following: given a mask and the number to be compressed, the bits of the number corresponding to the set mask bit are selected and compressed. 

Currently, this PR addresses only Java changes for compress bits operation. I've also updated the test framework.
Do review and share feedback.

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

Commit messages:
 - Compress bits implementation for byte/short/int/long

Changes: https://git.openjdk.java.net/panama-vector/pull/184/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=184&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8283598
  Stats: 17935 lines in 83 files changed: 17935 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/184.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/184/head:pull/184

PR: https://git.openjdk.java.net/panama-vector/pull/184