.Net: Fix Inline Functions Definition Extensions and add tests (#2366)

### Motivation and Context
This pull request introduces improvements to the Inline Functions
Definition Extensions Tests, adds a new test case for function calls
with input, and performs minor refactoring in the codebase. The changes
aim to enhance the test coverage and maintainability of the code.

Resolves #2361 

### Description
1. In
`dotnet/src/IntegrationTests/SkillDefinition/InlineFunctionsDefinitionExtensionsTests.cs`,
the `RedirectTextCompletion` class has been marked as `sealed` to
prevent further inheritance and improve performance.
2. A new test case, `ItSupportsFunctionCallsWithInput`, has been added
to
`dotnet/src/IntegrationTests/SkillDefinition/InlineFunctionsDefinitionExtensionsTests.cs`.
This test case checks if the function calls with input are supported
correctly.
3. In
`dotnet/src/SemanticKernel/SkillDefinition/InlineFunctionsDefinitionExtension.cs`,
the `InvokeAsync()` method has been replaced with
`kernel.RunAsync(skfunction)` to ensure proper execution of the semantic
function.
4. Minor formatting changes have been made to the code for better
readability and consistency.

### 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 😄

dotnet/samples/KernelSyntaxExamples/Example06_TemplateLanguage.cs

@@ -59,7 +59,7 @@ Is it weekend time (weekend/not weekend)?
 
         // Show the result
         Console.WriteLine("--- Semantic Function result");
-        var result = await kindOfDay.InvokeAsync();
+        var result = await kernel.RunAsync(kindOfDay);
         Console.WriteLine(result);
 
         /* OUTPUT:

dotnet/src/IntegrationTests/SkillDefinition/InlineFunctionsDefinitionExtensionsTests.cs

@@ -0,0 +1,104 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.SemanticKernel;
+using Microsoft.SemanticKernel.AI.TextCompletion;
+using Microsoft.SemanticKernel.Orchestration;
+using Microsoft.SemanticKernel.TemplateEngine;
+using SemanticKernel.IntegrationTests.Fakes;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace SemanticKernel.IntegrationTests.SkillDefinition;
+
+public sealed class InlineFunctionsDefinitionExtensionsTests : IDisposable
+{
+    public InlineFunctionsDefinitionExtensionsTests(ITestOutputHelper output)
+    {
+        this._logger = new RedirectOutput(output);
+        this._target = new PromptTemplateEngine();
+    }
+
+    [Fact]
+    public async Task ItSupportsFunctionCalls()
+    {
+        var builder = Kernel.Builder
+                .WithAIService<ITextCompletion>(null, new RedirectTextCompletion(), true)
+                .WithLogger(this._logger);
+        IKernel target = builder.Build();
+
+        var emailSkill = target.ImportSkill(new EmailSkillFake());
+
+        var prompt = "Hey {{_GLOBAL_FUNCTIONS_.GetEmailAddress}}";
+
+        // Act
+        SKContext actual = await target.InvokeSemanticFunctionAsync(prompt, maxTokens: 150);
+
+        // Assert
+        Assert.Null(actual.LastException);
+        Assert.False(actual.ErrorOccurred);
+        Assert.Equal("Hey johndoe1234@example.com", actual.Result);
+    }
+
+    [Fact]
+    public async Task ItSupportsFunctionCallsWithInput()
+    {
+        var builder = Kernel.Builder
+                .WithAIService<ITextCompletion>(null, new RedirectTextCompletion(), true)
+                .WithLogger(this._logger);
+        IKernel target = builder.Build();
+
+        var emailSkill = target.ImportSkill(new EmailSkillFake());
+
+        var prompt = "Hey {{_GLOBAL_FUNCTIONS_.GetEmailAddress \"a person\"}}";
+
+        // Act
+        SKContext actual = await target.InvokeSemanticFunctionAsync(prompt, maxTokens: 150);
+
+        // Assert
+        Assert.Null(actual.LastException);
+        Assert.False(actual.ErrorOccurred);
+        Assert.Equal("Hey a person@example.com", actual.Result);
+    }
+
+    private readonly RedirectOutput _logger;
+    private readonly PromptTemplateEngine _target;
+
+    public void Dispose()
+    {
+        this._logger.Dispose();
+    }
+
+    private sealed class RedirectTextCompletion : ITextCompletion
+    {
+        Task<IReadOnlyList<ITextResult>> ITextCompletion.GetCompletionsAsync(string text, CompleteRequestSettings requestSettings, CancellationToken cancellationToken)
+        {
+            return Task.FromResult<IReadOnlyList<ITextResult>>(new List<ITextResult> { new RedirectTextCompletionResult(text) });
+        }
+
+        IAsyncEnumerable<ITextStreamingResult> ITextCompletion.GetStreamingCompletionsAsync(string text, CompleteRequestSettings requestSettings, CancellationToken cancellationToken)
+        {
+            throw new NotImplementedException(); // TODO
+        }
+    }
+
+    internal sealed class RedirectTextCompletionResult : ITextResult
+    {
+        private readonly string _completion;
+
+        public RedirectTextCompletionResult(string completion)
+        {
+            this._completion = completion;
+        }
+
+        public ModelResult ModelResult => new(this._completion);
+
+        public Task<string> GetCompletionAsync(CancellationToken cancellationToken = default)
+        {
+            return Task.FromResult(this._completion);
+        }
+    }
+}

dotnet/src/SemanticKernel/SkillDefinition/InlineFunctionsDefinitionExtension.cs

@@ -145,7 +145,7 @@ public static Task<SKContext> InvokeSemanticFunctionAsync(
             frequencyPenalty,
             stopSequences);
 
-        return skfunction.InvokeAsync();
+        return kernel.RunAsync(skfunction);
     }
 
     private static string RandomFunctionName() => "func" + Guid.NewGuid().ToString("N");