* add subscription response

* fix send subscription response

* add register agent type response

* adding a test

* working on shaping up a test

* appsettins update for backend

* another appsettings

* fixup aspire hosting

* enable AGENT_HOST var from aspire

* add SendMessageAsync

* remove broken test

* test compiles and runs but is not (yet) correct

* subscriptions grain wireup.

* temp assert true.

* remove DI for SubscriptionGrain

* add xlang python code

* add subscription response

* rebond

* Update to .NET 9.0

* Fix Backend project SDK

* Package updates

* get RegisterAgentTypeRequest working

* fix exceptions

* add error handling for requests

* whoops

* send cloud event message type

* processing cloudevents

* trying tosend proto data - doesn't work

* trying to pack proto_data

* fix (#4238)

* pack the Message from agents_events

* format - not sure why these?

* format

* cleanup, error handling, xlang sample publishes messages that can be heard by .NET and vice versa

* format

* sdk version

* sdk vers

* net8

* back to net8

* remove netstandard2

* fix used

* remove unused

* more cleanup

* remove unneeded package

* I'm terrible at writing tests

* deserialize the cloud events and sent them as events

* comment

* cleanup

* await

* Delete dotnet/samples/Hello/Backend/Backend.csproj

unneeded change

* whoops

* merge main python back into here

* revert back to local

* revert some of the helloAgents changes.

* [.NET] Add happy path test for in-memory agent && Simplify HelloAgent example && some clean-up in extension APIs (#4227)

* add happy path test

* remove unnecessary namespace

* fix build error

* Update AgentBaseTests.cs

* revert changes

---------

* fix busted merge from main

* addressing review comments

* make internal

* case sensitive rename step 1

* case sensitive rename step 2

* remove!

---------

Co-authored-by: Peter Chang <petchang@microsoft.com>
Co-authored-by: Reuben Bond <reuben.bond@gmail.com>
Co-authored-by: Eric Zhu <ekzhu@users.noreply.github.com>
Co-authored-by: Xiaoyun Zhang <bigmiao.zhang@gmail.com>

closes #3950 closes #3702

What this is doing:

I am refactoring the services on the .NET runtime and attempting to clarify the naming and organization.
I added this doc to help capture the naming and concepts.
AgentRuntime / Worker should work similar to the python version and enables running the whole agent system in one process. For remote the system uses the versions of the services in the grpc folder.
lots of other bug fixes/threading cleanup - passing cancellation token throughout
Services update clarifies the naming and roles:

Worker: Hosts the Agents and is a client to the Gateway
Gateway:
-- RPC gateway for the other services APIs
-- Provides an RPC bridge between the workers and the Event Bus
Registry: keeps track of the agents in the system and which events they can handle
AgentState: persistent state for agents

* Wait for acknowledgment when sending message to gRPC channel

* Add CancellationToken parameters to API surface

* Clean up the Hello sample, support Aspire 9.0, & fix shutdown

* adds Orleans persistence for AgentState