.Net: Deprecated unused filter context classes (#6017)

### Motivation and Context

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Marked unused filter context classes as `Obsolete`.

### 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/src/SemanticKernel.Abstractions/Filters/Function/FunctionFilterContext.cs

@@ -1,5 +1,6 @@
 // Copyright (c) Microsoft. All rights reserved.
 
+using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 
@@ -9,6 +10,7 @@ namespace Microsoft.SemanticKernel;
 /// Base class with data related to function invocation.
 /// </summary>
 [Experimental("SKEXP0001")]
+[Obsolete("This class is deprecated in favor of FunctionInvocationContext class, which is used in IFunctionInvocationFilter interface.")]
 public abstract class FunctionFilterContext
 {
     /// <summary>

dotnet/src/SemanticKernel.Abstractions/Filters/Function/FunctionInvokedContext.cs

@@ -9,6 +9,7 @@ namespace Microsoft.SemanticKernel;
 /// Class with data related to function after invocation.
 /// </summary>
 [Experimental("SKEXP0001")]
+[Obsolete("This class is deprecated in favor of FunctionInvocationContext class, which is used in IFunctionInvocationFilter interface.")]
 public sealed class FunctionInvokedContext : FunctionFilterContext
 {
     /// <summary>

dotnet/src/SemanticKernel.Abstractions/Filters/Function/FunctionInvokingContext.cs

@@ -1,5 +1,6 @@
 // Copyright (c) Microsoft. All rights reserved.
 
+using System;
 using System.Diagnostics.CodeAnalysis;
 
 namespace Microsoft.SemanticKernel;
@@ -8,6 +9,7 @@ namespace Microsoft.SemanticKernel;
 /// Class with data related to function before invocation.
 /// </summary>
 [Experimental("SKEXP0001")]
+[Obsolete("This class is deprecated in favor of FunctionInvocationContext class, which is used in IFunctionInvocationFilter interface.")]
 public sealed class FunctionInvokingContext : FunctionFilterContext
 {
     /// <summary>

dotnet/src/SemanticKernel.Abstractions/Filters/Prompt/PromptFilterContext.cs

@@ -1,5 +1,6 @@
 // Copyright (c) Microsoft. All rights reserved.
 
+using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 
@@ -9,6 +10,7 @@ namespace Microsoft.SemanticKernel;
 /// Base class with data related to prompt rendering.
 /// </summary>
 [Experimental("SKEXP0001")]
+[Obsolete("This class is deprecated in favor of PromptRenderContext class, which is used in IPromptRenderFilter interface.")]
 public abstract class PromptFilterContext
 {
     /// <summary>

dotnet/src/SemanticKernel.Abstractions/Filters/Prompt/PromptRenderedContext.cs

@@ -1,5 +1,6 @@
 // Copyright (c) Microsoft. All rights reserved.
 
+using System;
 using System.Diagnostics.CodeAnalysis;
 
 namespace Microsoft.SemanticKernel;
@@ -8,6 +9,7 @@ namespace Microsoft.SemanticKernel;
 /// Class with data related to prompt after rendering.
 /// </summary>
 [Experimental("SKEXP0001")]
+[Obsolete("This class is deprecated in favor of PromptRenderContext class, which is used in IPromptRenderFilter interface.")]
 public sealed class PromptRenderedContext : PromptFilterContext
 {
     private string _renderedPrompt;

dotnet/src/SemanticKernel.Abstractions/Filters/Prompt/PromptRenderingContext.cs

@@ -1,5 +1,6 @@
 // Copyright (c) Microsoft. All rights reserved.
 
+using System;
 using System.Diagnostics.CodeAnalysis;
 
 namespace Microsoft.SemanticKernel;
@@ -8,6 +9,7 @@ namespace Microsoft.SemanticKernel;
 /// Class with data related to prompt before rendering.
 /// </summary>
 [Experimental("SKEXP0001")]
+[Obsolete("This class is deprecated in favor of PromptRenderContext class, which is used in IPromptRenderFilter interface.")]
 public sealed class PromptRenderingContext : PromptFilterContext
 {
     /// <summary>