RFR: 8281294: [vectorapi] FIRST_NONZERO reduction operation throws IllegalArgumentExcept on zero vectors

[Paul Sandoz]

…ArgumentExcept on zero vectors

This PR fixes issues for reduction using FIRST_NONZERO and add tests. The testing infrastructure is generalized to reduction functions and tests for min/max reductions are updated to use that.

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Commit messages:
 - 8281294: [vectorapi] FIRST_NONZERO reduction operation throws IllegalArgumentExcept on zero vectors

Changes: https://git.openjdk.java.net/jdk/pull/7410/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7410&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8281294
  Stats: 3725 lines in 54 files changed: 2742 ins; 407 del; 576 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7410.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7410/head:pull/7410

PR: https://git.openjdk.java.net/jdk/pull/7410