[vectorIntrinsics+mask] RFR: 8272745: VectorAPI: Vector/Mask type cleanup for masked vector intrinsics

[Eric Liu]

Some of the VectorAPIs were inconsistent with their intrinsic
declarations, and some of the type arguments were not precise enough as
well. E.g., The return type of "unaryOp" should be a subtype of "Vector"
instead of an all-purpose "Object" [1][2].

The imprecise declarations and type arguments would not effect the
correctness but bring bad readability and make the code hard to
maintain. This patch is a cleanup for those mismatched declarations of
VectorAPIs.

[1] https://github.com/openjdk/panama-vector/blob/vectorIntrinsics%2Bmask/src/java.base/share/classes/jdk/internal/vm/vector/VectorSupport.java#L269
[2] https://github.com/openjdk/panama-vector/blob/vectorIntrinsics%2Bmask/src/hotspot/share/classfile/vmIntrinsics.hpp#L812

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Commit messages:
 - 8272745: VectorAPI: Vector/Mask type cleanup for masked vector intrinsics

Changes: https://git.openjdk.java.net/panama-vector/pull/117/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=117&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8272745
  Stats: 250 lines in 4 files changed: 89 ins; 12 del; 149 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/117.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/117/head:pull/117

PR: https://git.openjdk.java.net/panama-vector/pull/117