Tracer should support trace exception count for specific entry or context

[sczyh30]

Issue Description

Type: enhancement

Describe what happened (or what feature you want)

Currently, we use Tracer.trace(xxx) to record the exception count. The trace method only supports tracing exception count for current entry in current context. In some circumstances this might not be enough. For example, in Dubbo adapter we generated two resources:

--SomeService
----SomeService:someMethod(xxx)

When biz exceptions are thrown, the Tracer.trace(xxx) can only add exception count for current entry (method entry), while the service entry is ignored. This causes the exception-based circuit breaking cannot take effect in the Dubbo service resource.

Describe what you expected to happen

The Tracer class should support trace exception count for specific entry or context. Adapters may improve their implementations.

Tell us your environment

Sentinel 1.4.1