adk-java: Contents.rearrangeEventsForAsyncFunctionResponsesInHistory method could generate duplicate function Response type event casusing message disorder, leading to model invocation failure.

[yuhao101]

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Describe the bug
Contents.rearrangeEventsForAsyncFunctionResponsesInHistory method could generate duplicate function Response type event, casusing message disorder, leading to model invocation failure.

To Reproduce
Steps to reproduce the behavior:
Bad case:
If filtered events order are FC1,FR1,FR2,FC2, after execute rearrangeEventsForAsyncFunctionResponsesInHistory we will get a new events list like: FC1,FR1,FR2,FC2,FR2; In this case, FR2 is added duplicate

Expected behavior
Add the following check code to avoid dupplicate adding.

Desktop (please complete the following information):

• OS: [e.g. iOS] macos
• Java version: 17
• ADK version(see maven dependency): 0.4.0

Additional context
Add any other context about the problem here.