热点参数限流是否支持对象类型参数？

## Issue Description

Type: *bug report* or *feature request*
feature request
### Describe what happened (or what feature you want)
目前使用1.6.3版本的Sentinel，发现热点参数限流参数类型只支持基本类型，后续版本是否支持对象类型参数呢？实际上web层或者dubbo层接口基本不会使用基本类型参数，接入热点参数限流代码侵入性较强

### 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 reviewing Sentinel 1.6.3 hotspot-parameter rate-limiting behavior and its web and Dubbo integration points. Clarify how object parameters should be identified and what compatibility is required; done means a documented decision and, if supported, verified object-parameter behavior.

Written by the indexing model from the issue text.