[vectorIntrinsics] RFR: 8283145: [vector] Add the compiler IR and aarch64 support for count leading and trailing zeros

[Xiaohong Gong]

This patch adds the hotspot compiler implementations for the vector operations of count leading and trailing zeros. It adds:
 - two vector nodes respectively for the two vector operations
 - the backend implementations for aarch64 NEON and SVE

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Commit messages:
 - 8283145: [vector] Add the compiler IR and aarch64 support for count leading and trailing zeros

Changes: https://git.openjdk.java.net/panama-vector/pull/180/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=180&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8283145
  Stats: 447 lines in 14 files changed: 325 ins; 0 del; 122 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/180.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/180/head:pull/180

PR: https://git.openjdk.java.net/panama-vector/pull/180