Fix DurationAttributeConverter negative fractional durations

[arnabnandy7]

Motivation and Context

Fixes #7060

DurationAttributeConverter incorrectly serialized negative fractional durations because Java represents them with negative seconds and positive nanos. For example, Duration.ofMillis(-1) was serialized as -1.999000000 instead of -0.001000000.

Modifications

Updated DurationAttributeConverter to correctly serialize negative fractional Duration values using their mathematical signed decimal representation.

Also updated parsing logic so number strings like -0.001000000 are converted back to negative durations instead of positive ones.

Added regression tests for:

• Negative fractional serialization
• Negative fractional parsing
• No-padding negative fractional parsing
• Duration round trips

Testing

Ran:

mvn -Dtest=DurationAttributeConverterTest test

Screenshots (if appropriate)

N/A

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• I have read the CONTRIBUTING document
• Local run of mvn install succeeds
• My code follows the code style of this project
• My change requires a change to the Javadoc documentation
• I have updated the Javadoc documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed
• I have added a changelog entry. Adding a new entry must be accomplished by running the scripts/new-change script and following the instructions. Commit the new file created by the script in .changes/next-release with your changes.
• My change is to implement 1.11 parity feature and I have updated LaunchChangelog

License

• I confirm that this pull request can be released under the Apache 2 license