.Net: Remove the experimental attribute from stable openapi api (#11745)

### Motivation, Context and Description

This PR removes the experimental attribute from the API that was
introduced a while ago and can be considered stable. Additionally, it
enables package validation.

Contributes to:
#10070

Author: SergeyMenshykh

dotnet/src/Functions/Functions.OpenApi/CompatibilitySuppressions.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- https://learn.microsoft.com/dotnet/fundamentals/package-validation/diagnostic-ids -->
+<Suppressions xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
+  <Suppression>
+    <DiagnosticId>CP0002</DiagnosticId>
+    <Target>F:Microsoft.SemanticKernel.Plugins.OpenApi.OpenApiKernelFunctionContext.KernelFunctionContextKey</Target>
+    <Left>lib/netstandard2.0/Microsoft.SemanticKernel.Plugins.OpenApi.dll</Left>
+    <Right>lib/net8.0/Microsoft.SemanticKernel.Plugins.OpenApi.dll</Right>
+  </Suppression>
+</Suppressions>

dotnet/src/Functions/Functions.OpenApi/Extensions/OpenApiFunctionExecutionParameters.cs

@@ -96,7 +96,6 @@ public class OpenApiFunctionExecutionParameters
     /// <summary>
     /// A custom REST API parameter filter.
     /// </summary>
-    [Experimental("SKEXP0040")]
     public RestApiParameterFilter? ParameterFilter { get; set; }
 
     /// <summary>
@@ -119,7 +118,6 @@ public class OpenApiFunctionExecutionParameters
     /// <param name="enablePayloadNamespacing">Determines whether payload parameter names are augmented with namespaces.
     /// Namespaces prevent naming conflicts by adding the parent parameter name as a prefix, separated by dots.</param>
     /// <param name="operationsToExclude">Optional list of operations not to import, e.g. in case they are not supported</param>
-    [Experimental("SKEXP0040")]
     public OpenApiFunctionExecutionParameters(
         HttpClient? httpClient = null,
         AuthenticateRequestAsyncCallback? authCallback = null,

dotnet/src/Functions/Functions.OpenApi/Functions.OpenApi.csproj

@@ -5,6 +5,7 @@
     <RootNamespace>$(AssemblyName)</RootNamespace>
     <TargetFrameworks>net8.0;netstandard2.0</TargetFrameworks>
     <NoWarn>$(NoWarn);SKEXP0040</NoWarn>
+    <EnablePackageValidation>true</EnablePackageValidation>
   </PropertyGroup>
   <Import Project="$(RepoRoot)/dotnet/nuget/nuget-package.props" />
   <Import Project="$(RepoRoot)/dotnet/src/InternalUtilities/src/InternalUtilities.props" />

dotnet/src/Functions/Functions.OpenApi/Model/RestApiExpectedResponse.cs

@@ -1,13 +1,10 @@
 // Copyright (c) Microsoft. All rights reserved.
 
-using System.Diagnostics.CodeAnalysis;
-
 namespace Microsoft.SemanticKernel.Plugins.OpenApi;
 
 /// <summary>
 /// REST API response.
 /// </summary>
-[Experimental("SKEXP0040")]
 public sealed class RestApiExpectedResponse
 {
     /// <summary>

dotnet/src/Functions/Functions.OpenApi/Model/RestApiInfo.cs

@@ -1,13 +1,10 @@
 // Copyright (c) Microsoft. All rights reserved.
 
-using System.Diagnostics.CodeAnalysis;
-
 namespace Microsoft.SemanticKernel.Plugins.OpenApi;
 
 /// <summary>
 /// The REST API information.
 /// </summary>
-[Experimental("SKEXP0040")]
 public sealed class RestApiInfo
 {
     /// <summary>

dotnet/src/Functions/Functions.OpenApi/Model/RestApiOAuthFlow.cs

@@ -3,14 +3,12 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
-using System.Diagnostics.CodeAnalysis;
 
 namespace Microsoft.SemanticKernel.Plugins.OpenApi;
 
 /// <summary>
 /// REST API OAuth Flow.
 /// </summary>
-[Experimental("SKEXP0040")]
 public sealed class RestApiOAuthFlow
 {
     /// <summary>

dotnet/src/Functions/Functions.OpenApi/Model/RestApiOAuthFlows.cs

@@ -1,13 +1,10 @@
 // Copyright (c) Microsoft. All rights reserved.
 
-using System.Diagnostics.CodeAnalysis;
-
 namespace Microsoft.SemanticKernel.Plugins.OpenApi;
 
 /// <summary>
 /// REST API OAuth Flows.
 /// </summary>
-[Experimental("SKEXP0040")]
 public sealed class RestApiOAuthFlows
 {
     /// <summary>

dotnet/src/Functions/Functions.OpenApi/Model/RestApiOperation.cs

@@ -3,7 +3,6 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
-using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Net.Http;
 using System.Text.Json.Nodes;
@@ -14,7 +13,6 @@ namespace Microsoft.SemanticKernel.Plugins.OpenApi;
 /// <summary>
 /// The REST API operation.
 /// </summary>
-[Experimental("SKEXP0040")]
 public sealed class RestApiOperation
 {
     /// <summary>

dotnet/src/Functions/Functions.OpenApi/Model/RestApiParameter.cs

@@ -1,13 +1,10 @@
 // Copyright (c) Microsoft. All rights reserved.
 
-using System.Diagnostics.CodeAnalysis;
-
 namespace Microsoft.SemanticKernel.Plugins.OpenApi;
 
 /// <summary>
 /// REST API parameter.
 /// </summary>
-[Experimental("SKEXP0040")]
 public sealed class RestApiParameter
 {
     /// <summary>

dotnet/src/Functions/Functions.OpenApi/Model/RestApiParameterLocation.cs

@@ -1,13 +1,10 @@
 // Copyright (c) Microsoft. All rights reserved.
 
-using System.Diagnostics.CodeAnalysis;
-
 namespace Microsoft.SemanticKernel.Plugins.OpenApi;
 
 /// <summary>
 /// REST API parameter location.
 /// </summary>
-[Experimental("SKEXP0040")]
 public enum RestApiParameterLocation
 {
     /// <summary>