Remove HACK that used to put `Handle` in config bag (#2806)

## Motivation and Context
Removes `HACK` that used to put `Handle` in config bag.

## Description
The `HACK` was previously placed in `ServiceRuntimePlugin::config`
because later in the orchestrator execution, we needed to access service
config fields (through `Handle`) to build endpoint `Params` within
`EndpointParamsInterceptor`. Now that service config fields are baked
into a frozen layer, `EndpointParamsInterceptor` can load those fields
directly from the config bag (to which the frozen layer has been added)
when constructing endpoint `Params`. We can therefore remove `HACK` at
this point.

## Testing
- [x] Passed tests in CI

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Co-authored-by: Yuki Saito <awsaito@amazon.com>