RFR: 8371768: AArch64: test/hotspot/jtreg/compiler/loopopts/superword/TestReductions.java fails on SVE after JDK-8340093

[Aleksey Shipilev]

Looks like the test should be more resilient with UseSVE > 0, which _can_ vectorise. It does not look all that reliable to me to failOn when vectorization actually happens. So I dropped some non-arch-specific rules, and amended AArch64-specific rules for UseSVE.

Testing:
 - [x] Linux AArch64 server fastdebug, affected test on machine with UseSVE=1 by default
 - [x] Linux AArch64 server fastdebug, affected test on machine with UseSVE=0 overridden

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Commit messages:
 - A bit of mop up
 - UseSVE works

Changes: https://git.openjdk.org/jdk/pull/28423/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28423&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8371768
  Stats: 163 lines in 1 file changed: 16 ins; 89 del; 58 mod
  Patch: https://git.openjdk.org/jdk/pull/28423.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28423/head:pull/28423

PR: https://git.openjdk.org/jdk/pull/28423