RFR: 8367942: Add API note discussing Double.compareTo total order and IEEE 754 total order

[Joe Darcy]

Add a total that the total order used by {Double, Float}.compareTo is different than the total order defined by IEEE 754, starting the 2008 version of that standard.

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Commit messages:
 - JDK-8367942: Add API note discussing Double.compareTo total order and IEEE 754 total order

Changes: https://git.openjdk.org/jdk/pull/27356/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27356&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8367942
  Stats: 20 lines in 3 files changed: 19 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/27356.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27356/head:pull/27356

PR: https://git.openjdk.org/jdk/pull/27356