[vectorIntrinsics] RFR: 8281562:[vectorapi] Add support for popcount operation [v2]

[Smita Kamath]

> 8281562:[vectorapi] Add support for popcount operation

Smita Kamath has updated the pull request incrementally with one additional commit since the last revision:

  Fixed review comments. Added test case to the test framework

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Changes:
  - all: https://git.openjdk.java.net/panama-vector/pull/173/files
  - new: https://git.openjdk.java.net/panama-vector/pull/173/files/5161759a..f594bea9

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=173&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=173&range=00-01

  Stats: 1120 lines in 73 files changed: 972 ins; 78 del; 70 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/173.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/173/head:pull/173

PR: https://git.openjdk.java.net/panama-vector/pull/173