.Net: Small improvements in Structured Outputs (#9906)

### Motivation and Context

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Resolves: #9897

This PR addresses remaining comments from previous PR related to
Structured Outputs:
#9873.

### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

Author: dmytrostruk

dotnet/samples/Concepts/ChatCompletion/OpenAI_StructuredOutputs.cs

@@ -299,10 +299,7 @@ public async Task StructuredOutputsWithFunctionsFromYamlAsync()
         var functionPath = Path.Combine(Directory.GetCurrentDirectory(), "Resources", "Plugins", "MoviePlugins", "MoviePluginYaml", "TopMovies.yaml");
 
         // Load YAML prompt.
-        using Stream stream = File.OpenRead(functionPath);
-        using StreamReader reader = new(stream);
-
-        var topMoviesYaml = reader.ReadToEnd();
+        var topMoviesYaml = File.ReadAllText(functionPath);
 
         // Import a function from YAML.
         var function = kernel.CreateFunctionFromPromptYaml(topMoviesYaml);

dotnet/src/Connectors/Connectors.OpenAI.UnitTests/Helpers/OpenAIChatResponseFormatHelperTests.cs renamed to dotnet/src/Connectors/Connectors.OpenAI.UnitTests/Helpers/OpenAIChatResponseFormatBuilderTests.cs

@@ -10,13 +10,13 @@
 namespace SemanticKernel.Connectors.OpenAI.UnitTests.Helpers;
 
 /// <summary>
-/// Unit tests for <see cref="OpenAIChatResponseFormatHelper"/> class.
+/// Unit tests for <see cref="OpenAIChatResponseFormatBuilder"/> class.
 /// </summary>
-public sealed class OpenAIChatResponseFormatHelperTests
+public sealed class OpenAIChatResponseFormatBuilderTests
 {
     private readonly JsonSerializerOptions _options = new();
 
-    public OpenAIChatResponseFormatHelperTests()
+    public OpenAIChatResponseFormatBuilderTests()
     {
         this._options.Converters.Add(new BinaryDataJsonConverter());
     }
@@ -33,7 +33,7 @@ public void GetJsonSchemaResponseFormatReturnsChatResponseFormatByDefault(
         var jsonElement = jsonDocument.RootElement;
 
         // Act
-        var chatResponseFormat = OpenAIChatResponseFormatHelper.GetJsonSchemaResponseFormat(jsonElement);
+        var chatResponseFormat = OpenAIChatResponseFormatBuilder.GetJsonSchemaResponseFormat(jsonElement);
         var responseFormat = this.GetResponseFormat(chatResponseFormat);
 
         // Assert
@@ -79,7 +79,7 @@ public void GetJsonSchemaResponseFormatThrowsExceptionWhenSchemaDoesNotExist()
         var jsonElement = jsonDocument.RootElement;
 
         // Act & Assert
-        Assert.Throws<ArgumentException>(() => OpenAIChatResponseFormatHelper.GetJsonSchemaResponseFormat(jsonElement));
+        Assert.Throws<ArgumentException>(() => OpenAIChatResponseFormatBuilder.GetJsonSchemaResponseFormat(jsonElement));
     }
 
     public static TheoryData<string, string, bool?> ChatResponseFormatJson => new()

dotnet/src/Connectors/Connectors.OpenAI/Core/ClientCore.ChatCompletion.cs

@@ -540,10 +540,10 @@ protected virtual ChatCompletionOptions CreateChatCompletionOptions(
                     }
                 }
 
-                return OpenAIChatResponseFormatHelper.GetJsonSchemaResponseFormat(formatElement);
+                return OpenAIChatResponseFormatBuilder.GetJsonSchemaResponseFormat(formatElement);
 
             case Type formatObjectType:
-                return OpenAIChatResponseFormatHelper.GetJsonSchemaResponseFormat(formatObjectType);
+                return OpenAIChatResponseFormatBuilder.GetJsonSchemaResponseFormat(formatObjectType);
         }
 
         return null;

dotnet/src/Connectors/Connectors.OpenAI/Helpers/OpenAIChatResponseFormatHelper.cs renamed to dotnet/src/Connectors/Connectors.OpenAI/Helpers/OpenAIChatResponseFormatBuilder.cs

@@ -9,9 +9,9 @@
 namespace Microsoft.SemanticKernel.Connectors.OpenAI;
 
 /// <summary>
-/// Helper class to process <see cref="ChatResponseFormat"/> object.
+/// Helper class to build <see cref="ChatResponseFormat"/> object.
 /// </summary>
-internal static class OpenAIChatResponseFormatHelper
+internal static class OpenAIChatResponseFormatBuilder
 {
     /// <summary>
     /// <see cref="JsonSchemaMapperConfiguration"/> for JSON schema format for structured outputs.