Feign降级的支持粒度，能否支持服务粒度(Can feign support service granularity)

## Issue Description
Feign限流降级好像只支持url粒度，能否支持服务粒度，就像对RestTemplate支持两种粒度一样(Feign's current limiting degradation seems to only support URL granularity. Can it support service granularity, just like resttemplate supports two kinds of granularity

Type: *bug report* or *feature request*

### Describe what happened (or what feature you want)

### Describe what you expected to happen

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

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### Tell us your environment

### Anything else we need to know?

Start by comparing Feign's current URL-granularity limiting and degradation behavior with the two granularity modes described for RestTemplate. Define the intended service-granularity behavior and verify it with focused Feign integration tests; done means Feign supports both URL and service granularity.

Written by the indexing model from the issue text.