Change one timeline field trigger validation on both

[zhangxiaoxing]

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• ISSUE (if exists) DESCRIPTIVE_SUMMARY_OF_CHANGES
• Overlooked validation updates on the paired text field in the timeline custom bounds dialog #2854 Fix issue with overlooked timeline field validation

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Description

• Overlooked validation updates on the paired text field in the timeline custom bounds dialog #2854 Fix issue with overlooked timeline field validation
• Trigger validation on the paired timeline Interval Start or End fields upon change of a single field, by calling the relevant setText() method.
• A 200ms latency is added to handle the intricate and nested validation logic in external dependencies.

Checklist

• Merged with master beforehand

Added tests?

• 👍 yes
• 🙅 no, because they aren't needed

Added to documentation?

• 👍 README.md
• 👍 API Changes
• 👍 Additional documentation in docs
• 👍 Relevant code documentation
• 🙅 no, because they aren’t needed