Add UT to verify TIMEOUT_FILTER_START_TIME attachement removal in case of exception

[khanimteyaz]

Write an UT to verify removal of TIMEOUT_FILTER_START_TIME attachement in case if exception occurs
in dubbo-rpc/dubbo-rpc-api/src/main/java/org/apache/dubbo/rpc/filter/TimeoutFilter.java.

This task is an extension to add UT for PR #3174

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Environment

• Dubbo version: xxx
• Operating System version: xxx
• Java version: xxx

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1. xxx
2. xxx
3. xxx

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Expected Result

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Actual Result

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