.NET: [BREAKING] Rename GetNewSession to CreateSession (#3501)

* Rename GetNewSession to CreateSession

* Address copilot feedback

* Suppress warning

* Suppress warning

* Fix further warnings.

dotnet/samples/GettingStarted/Workflows/Agents/CustomAgentExecutors/Program.cs

@@ -136,7 +136,7 @@ internal sealed class SloganWriterExecutor : Executor
 
     public async ValueTask<SloganResult> HandleAsync(string message, IWorkflowContext context, CancellationToken cancellationToken = default)
     {
-        this._session ??= await this._agent.GetNewSessionAsync(cancellationToken);
+        this._session ??= await this._agent.CreateSessionAsync(cancellationToken);
 
         var result = await this._agent.RunAsync(message, this._session, cancellationToken: cancellationToken);
 
@@ -209,7 +209,7 @@ internal sealed class FeedbackExecutor : Executor<SloganResult>
 
     public override async ValueTask HandleAsync(SloganResult message, IWorkflowContext context, CancellationToken cancellationToken = default)
     {
-        this._session ??= await this._agent.GetNewSessionAsync(cancellationToken);
+        this._session ??= await this._agent.CreateSessionAsync(cancellationToken);
 
         var sloganMessage = $"""
             Here is a slogan for the task '{message.Task}':

dotnet/samples/GettingStarted/Workflows/Agents/WorkflowAsAnAgent/Program.cs

@@ -37,7 +37,7 @@ public static class Program
         // Create the workflow and turn it into an agent
         var workflow = WorkflowFactory.BuildWorkflow(chatClient);
         var agent = workflow.AsAgent("workflow-agent", "Workflow Agent");
-        var session = await agent.GetNewSessionAsync();
+        var session = await agent.CreateSessionAsync();
 
         // Start an interactive loop to interact with the workflow as if it were an agent
         while (true)

dotnet/samples/GettingStarted/Workflows/Declarative/HostedWorkflow/Program.cs

@@ -47,7 +47,7 @@ internal sealed class Program
 
         AIAgent agent = aiProjectClient.AsAIAgent(agentVersion);
 
-        AgentSession session = await agent.GetNewSessionAsync();
+        AgentSession session = await agent.CreateSessionAsync();
 
         ProjectConversation conversation =
             await aiProjectClient

dotnet/samples/GettingStarted/Workflows/Observability/WorkflowAsAnAgent/Program.cs

@@ -90,7 +90,7 @@ public static class Program
         {
             EnableSensitiveData = true  // enable sensitive data at the agent level such as prompts and responses
         };
-        var session = await agent.GetNewSessionAsync();
+        var session = await agent.CreateSessionAsync();
 
         // Start an interactive loop to interact with the workflow as if it were an agent
         while (true)