[vectorIntrinsics] RFR: 8263424: Extend vector size support for SVE

[Ningsheng Jian]

This patch adds support of vector operations with size less than MaxVectorSize for SVE. Basically, for general vector operations, we simply keep original operations, i.e. doing a full vector length operations, but for load/store and reduction operations, we use
predicate operations to make sure only vector elements in the size limit are loaded/stored/calculated.

This patch also fixes an SVE load/store addressing mode usage issue. For SVE load/store scalar plus immediate, the immediate displacements are calculated by both vector element size and memory element size. As the existing vmemA_immIOffset4 and vmemA_immLOffset4 does not take into account of the vector and memory element size difference, we should not use them for extend/narrow forms.

Tested with tier1 and jdk:tier3. jdk/incubator/vector cases have also been verified with different MaxVectorSize options.

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Commit messages:
 - 8263424: Extend vector size support for SVE

Changes: https://git.openjdk.java.net/panama-vector/pull/49/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=49&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263424
  Stats: 1123 lines in 5 files changed: 661 ins; 29 del; 433 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/49.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/49/head:pull/49

PR: https://git.openjdk.java.net/panama-vector/pull/49