[vectorIntrinsics] RFR: 8265916: Add StoreVectorScatter nodes implementation for Arm SVE [v3]

[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

Wang Huang has updated the pull request incrementally with two additional commits since the last revision:

 - add m4 file
 - add case for partial

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Changes:
  - all: https://git.openjdk.java.net/panama-vector/pull/73/files
  - new: https://git.openjdk.java.net/panama-vector/pull/73/files/c3742456..a4d7590a

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=73&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=73&range=01-02

  Stats: 8 lines in 2 files changed: 8 ins; 0 del; 0 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