[vectorIntrinsics+mask] RFR: 8274236: Cleanups related to X86 masking support.

[Jatin Bhateja]

- Re-factor and cleanup existing VectorLoadMask, VectorStoreMask and CICS patterns (one source is memory operand).

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Commit messages:
 - 8274236: Cleanups related to X86 masking support.

Changes: https://git.openjdk.java.net/panama-vector/pull/131/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=131&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274236
  Stats: 185 lines in 7 files changed: 20 ins; 73 del; 92 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/131.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/131/head:pull/131

PR: https://git.openjdk.java.net/panama-vector/pull/131