Rysweet 5201 refactor runtime interface

[rysweet]

Changes to align the .NET code more with the python codebase.

• rename *Worker to *Runtime
• refactor shared runtime elements to AgentRuntimeBase
• align runtime interface with python

Why are these changes needed?

Aligning the .NET with the python code and then we can evolve together from there.

Related issue number

Closes #5201

Copilot reviewed 5 out of 18 changed files in this pull request and generated no comments.

Files not reviewed (13)

• dotnet/src/Microsoft.AutoGen/Core/AgentWorker.cs: Evaluated as low risk
• dotnet/src/Microsoft.AutoGen/Core/IAgentWorker.cs: Evaluated as low risk
• dotnet/src/Microsoft.AutoGen/Agents/IOAgent/WebAPIAgent/WebAPIAgent.cs: Evaluated as low risk
• dotnet/src/Microsoft.AutoGen/Core.Grpc/App.cs: Evaluated as low risk
• dotnet/src/Microsoft.AutoGen/Core/IAgentRuntimeExtensions.cs: Evaluated as low risk
• dotnet/samples/dev-team/DevTeam.Backend/Program.cs: Evaluated as low risk
• dotnet/src/Microsoft.AutoGen/Core/HostBuilderExtensions.cs: Evaluated as low risk
• dotnet/test/Microsoft.AutoGen.Core.Tests/AgentTests.cs: Evaluated as low risk
• dotnet/src/Microsoft.AutoGen/Core/AgentExtensions.cs: Evaluated as low risk
• dotnet/test/Microsoft.AutoGen.Core.Grpc.Tests/AgentGrpcTests.cs: Evaluated as low risk
• dotnet/src/Microsoft.AutoGen/Core.Grpc/GrpcAgentWorkerHostBuilderExtension.cs: Evaluated as low risk
• dotnet/src/Microsoft.AutoGen/Core/App.cs: Evaluated as low risk
• dotnet/src/Microsoft.AutoGen/Core.Grpc/GrpcAgentRuntime.cs: Evaluated as low risk

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.08%. Comparing base (138913b) to head (c2646c4).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5204   +/-   ##
=======================================
  Coverage   70.08%   70.08%           
=======================================
  Files         179      179           
  Lines       11619    11619           
=======================================
  Hits         8143     8143           
  Misses       3476     3476           

Flag	Coverage Δ
unittests	70.08% <ø> (ø)

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