[vectorIntrinsics] RFR: 8271009: AArch64: Wrap duplicated SVE instructions into a single method

[Eric Liu]

This patch is a small cleanup. Since most of the usage of 'sve_whilelo'
are a pair of 'mov' and 'whilelo', this patch wraps them as a single
method.

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Commit messages:
 - 8271009: AArch64: Wrap duplicated SVE instructions into a single method

Changes: https://git.openjdk.java.net/panama-vector/pull/101/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=101&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8271009
  Stats: 190 lines in 3 files changed: 20 ins; 87 del; 83 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/101.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/101/head:pull/101

PR: https://git.openjdk.java.net/panama-vector/pull/101