[vectorIntrinsics] RFR: Conversion test refactor

[Paul Sandoz]

Completes the refactor of the conversions tests, using a data provider rather than explicit methods. Compilation characteristics should be similar, as the kernel methods are still called the same number of times.

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Commit messages:
 - Use data providers
 - Merge branch 'vectorIntrinsics' into conversion-test-refactor
 - Refactor reinterpret_kernel
 - Merge remote-tracking branch 'upstream/vectorIntrinsics' into conversion-test-refactor
 - Refactor tests to be faster.

Changes: https://git.openjdk.java.net/panama-vector/pull/23/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=23&range=00
  Stats: 22307 lines in 6 files changed: 60 ins; 22096 del; 151 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/23.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/23/head:pull/23

PR: https://git.openjdk.java.net/panama-vector/pull/23