Issue Description

In sentinel-core moudle, there are many functional interfaces, such as Function , Consumer , BiConsumer , etc. they are all copied JDK8. I guess these functional interfaces were created because sentinel used a JDK version lower than 8, but we wanted to use functional interfaces. But now, sentinel depends on the JDK version. The minimum requirement is 8. Therefore, we can delete these interfaces and use the interfaces provided by JDK.

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