Split AzureServiceFabric into multiple projects

DurableTask.AzureServiceFabric contains multiple logical units in a single project:

- The core implementation of IOrchestrationServiceClient and IOrchestrationService on top of Service Fabric reliable collections.
- The Service Fabric stateful service exposing the orchestration service over Web API
- The remote client implementing IOrchestrationServiceClient communicating with the Web API

This brings some difficulties, the main ones are:

1. The current implementation detail of the Service Fabric stateful service requires .NET Framework, which prohibits using the core part or the remote client in .NET 5/6 or .NET Core environments.
2. The consumer of the remote client gets a lot of dependencies which are useless from the remote client prospective.

Proposed split:

- DurableTask.AzureServiceFabric.Core - contains the core implementation
- DurableTask.AzureServiceFabric.Service - contains Service Fabric stateful service
- DurableTask.AzureServiceFabric.Client - contains the remote client
- DurableTask.AzureServiceFabric - empty project for the backward compatibility referencing all above mentioned projects (NuGets)