refactor: remove unused files per PR feedback

Author: AlexDaines

sdk/src/Core/Amazon.Runtime/ClientConfigExtensions.cs

@@ -398,6 +398,28 @@ public partial interface IClientConfig
         /// </summary>
         ResponseChecksumValidation ResponseChecksumValidation { get; }
 
+        /// <summary>
+        /// Gets or sets the authentication scheme preference for this client configuration.
+        /// <para>
+        /// This property allows you to specify a comma-separated preference list of authentication schemes
+        /// (e.g., "sigv4a,sigv4") that will be used to reprioritize the supported authentication schemes for this client.
+        /// If not set, the client will use environment variables, configuration files,
+        /// or fall back to the default model-based authentication scheme resolution.
+        /// </para>
+        /// </summary>
+        string AuthSchemePreference { get; }
+
+        /// <summary>
+        /// Gets or sets the SigV4a signing region set for this client.
+        /// <para>
+        /// This property allows you to specify a comma-separated list of regions (e.g., "us-east-1,us-west-2")
+        /// that will be used for SigV4a signing. The region set determines which regions the signed request is valid for.
+        /// If not set, the client will use environment variables, configuration files,
+        /// endpoints metadata, or fall back to the client's configured region.
+        /// </para>
+        /// </summary>
+        string SigV4aSigningRegionSet { get; }
+
 
 
         /// <summary>

sdk/src/Core/Amazon.Runtime/IAuthSchemeResolver.cs

@@ -364,7 +364,7 @@ protected virtual List<IAuthSchemeOption> ApplyAuthSchemePreferences(IClientConf
         private string ResolveAuthSchemePreference(IClientConfig clientConfig)
         {
             // Check for legacy SignatureMethod configuration (backwards compatibility for S3)
-            if (clientConfig?.SignatureMethod != null && clientConfig.GetIsSignatureMethodExplicitlySet())
+            if (clientConfig?.SignatureMethod != null && (clientConfig as ClientConfig)?.IsSignatureMethodExplicitlySet == true)
             {
                 bool isS3Service = clientConfig.ServiceId?.Equals("S3", StringComparison.OrdinalIgnoreCase) == true ||
                                   clientConfig.ServiceId?.Equals("S3 Control", StringComparison.OrdinalIgnoreCase) == true;
@@ -383,7 +383,7 @@ private string ResolveAuthSchemePreference(IClientConfig clientConfig)
             }
 
             // Client configuration
-            string clientPreference = clientConfig?.GetAuthSchemePreference();
+            string clientPreference = clientConfig?.AuthSchemePreference;
             if (!string.IsNullOrWhiteSpace(clientPreference))
             {
                 Logger.InfoFormat("Using auth scheme preference from client configuration: {0}", clientPreference);