AnimatorStateTransition add hasExitTime, fixedDuration, setTrigger

[luzhuang]

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• [x] The commit message follows our guidelines
• [ ] Tests for the changes have been added (for bug fixes / features)
• [ ] Docs have been added / updated (for bug fixes / features)

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Summary by CodeRabbit

• New Features

  • Enhanced animation control with new methods for managing trigger states.
  • Added ability to specify parameters as triggers in the AnimatorController.
  • Introduced new methods for clearing transitions in the AnimatorStateMachine.

• Improvements

  • Refined transition management logic for better handling of exit times.
  • Enhanced documentation for AnimatorStateMachine methods.

• Tests

  • Expanded test cases to include new scenarios with parameter settings and transitions.