[vectorIntrinsics] RFR: 8265916: Add StoreVectorScatter nodes implementation for Arm SVE

[Wang Huang]

* add `sve_st1w_scatter` and `sve_st1w_scatter`
* implement `scatterI` and `scatterL`
* `load gather partial` and `store scatter partial` are not contained in this patch, and they will be in next patches

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

Commit messages:
 - 8265916: Add StoreVectorScatter nodes implementation for Arm SVE

Changes: https://git.openjdk.java.net/panama-vector/pull/73/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=73&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8265916
  Stats: 130 lines in 5 files changed: 64 ins; 2 del; 64 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/73.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/73/head:pull/73

PR: https://git.openjdk.java.net/panama-vector/pull/73