RFR: 8374785: Template Library: need to tag Float16.copySign as having non-deterministic result because of multiple NaNs with different sign bits

[Emanuel Peter]

This is a very similar issue as https://github.com/openjdk/jdk/pull/29033 / [JDK-8374489](https://bugs.openjdk.org/browse/JDK-8374489).

There are `NaN` encodings that have the sign bit set, and others that have it not set.
If we now copy the sign from such a `NaN` to a numeric value (e.g. `1`), we can get `1` or `-1`.


jshell> var a = Float.NaN;
a ==> NaN
jshell> var b = Float.intBitsToFloat(0xFFC00000);
b ==> NaN
jshell> Math.copySign(1f, a)
==> 1.0
jshell> Math.copySign(1f, b)
==> -1.0
jshell> Float16.copySign(Float16.valueOf(1f), Float16.valueOf(a))
==> 1.0
jshell> Float16.copySign(Float16.valueOf(1f), Float16.valueOf(b))
==> -1.0


Since `NaN` values of different encodings are interchangable, and we cannot know what `NaN` we get, and hence the sign bit is arbitrary, we can also not know the sign of the result of `Float16.copySign`. We have to mark it as non-deterministic and hence disable result verification.

Since this is a test-bug, I have no regression test. But I verified it manually, that with the same seed (for the ExpressionFuzzer) that fails before this change, we now succeed after the change.

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Commit messages:
 - JDK-8374785

Changes: https://git.openjdk.org/jdk/pull/29118/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29118&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8374785
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/29118.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29118/head:pull/29118

PR: https://git.openjdk.org/jdk/pull/29118