[vectorIntrinsics] RFR: 8269264: Some more cleanups for Vector API SVE support

[Ningsheng Jian]

Some more vectorIntrinsics SVE codegen cleanups for preparing a further
review patch in jdk mainline. This change includes:

1. Incorporate changes while preparing jdk mainline PR [1], which
includes some minor style changes and extending SVE vector size to
support 8 bytes to achieve better performance for *64Vector operations
and shuffles.
2. Fix register effects in some VectorCast rules, spotted by @XiaohongGong,
to avoid register reuse problem.
3. Merge reduction rules, as of what have been done for partial sizes.
4. Sort VectorCast rules by types/names for easier review.
5. Move sve_compare() from ad file to c2_MacroAssembler just as
recently added neon_compare().

[1] https://github.com/openjdk/jdk/pull/4122

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Commit messages:
 - 8269264: Some more cleanups for Vector API SVE support

Changes: https://git.openjdk.java.net/panama-vector/pull/94/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=94&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8269264
  Stats: 1942 lines in 7 files changed: 492 ins; 923 del; 527 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/94.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/94/head:pull/94

PR: https://git.openjdk.java.net/panama-vector/pull/94