Refactor interceptor phases to improve optionality inside interceptors (#2670)

## Motivation and Context
This PR:
- Deletes `TraceProbe`
- Replaces the orchestrator's `Phase` helper with a couple of macros
- Introduces the concept of phases into `InterceptorContext` so that
input/output/error/request/response accessors don't need option wrappers
- Adds `TypeErasedError` so that `orchestrator::Error` can implement
`Error`
- Rewinds the interceptor context in the retry loop

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