Expand more statistic dimensions( such as 20s, 1min, 20min), not only for 1 second | 流控规则支持自定义统计时长

## Issue Description

*feature request*

### Describe what happened (or what feature you want)
In some situation, we want to perform flow control not only based on the statistics of 1 second. For example, as for some origin/callers, we wanna count the call times in 1 minute and block the caller if the count exceeds the threshold. Sentinel does not support this kind of statistics.

### Describe what you expected to happen
Sentinel supports more statistic dimension of unit. It would be perfect if programmers can build the statistic rule by setting count parameters.

### How to reproduce it (as minimally and precisely as possible)

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### Tell us your environment

### Anything else we need to know?

The issue does not name any files, tests, or entry points. Start by locating Sentinel's statistic and flow-control implementation, then define how configurable windows such as 20 seconds, 1 minute, and 20 minutes should be represented and verified; done means rules can count within those configured durations and enforce their thresholds.

Written by the indexing model from the issue text.