RFR: JDK-8302800: Augment NaN handling tests of FDLIBM methods

[Joe Darcy]

Augment NaN-handling tests to include exotic NaN bit patterns. Assuming this changeset goes back first, I'll update https://github.com/openjdk/jdk/pull/12608 to follow the same convention afterward.

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Commit messages:
 - JDK-8302800: Augment NaN handling tests of FDLIBM methods

Changes: https://git.openjdk.org/jdk/pull/12644/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12644&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8302800
  Stats: 198 lines in 7 files changed: 94 ins; 79 del; 25 mod
  Patch: https://git.openjdk.org/jdk/pull/12644.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12644/head:pull/12644

PR: https://git.openjdk.org/jdk/pull/12644