fix: set use_aws_shared_config_files opts-in

This change makes the ConfigurationResolver to load configuration from aws shared config files based on the configuration `use_aws_shared_config_files` either provided as provider arguments or as service client arguments.

src/Credentials/InstanceProfileProvider.php

@@ -60,6 +60,9 @@ class InstanceProfileProvider
     /** @var string */
     private $endpointMode;
 
+    /** @var bool */
+    private $useAwsSharedConfigFiles;
+
     /**
      * The constructor accepts the following options:
      *
@@ -88,6 +91,7 @@ public function __construct(array $config = [])
         }
 
         $this->endpointMode = $config[self::CFG_EC2_METADATA_SERVICE_ENDPOINT_MODE] ?? null;
+        $this->useAwsSharedConfigFiles = $config['use_aws_shared_config_files'] ?? false;
     }
 
     /**
@@ -344,7 +348,7 @@ private function shouldFallbackToIMDSv1(): bool
                     self::CFG_EC2_METADATA_V1_DISABLED,
                     self::DEFAULT_AWS_EC2_METADATA_V1_DISABLED,
                     'bool',
-                    ['use_aws_shared_config_files' => true]
+                    ['use_aws_shared_config_files' => $this->useAwsSharedConfigFiles]
                 )
             )
             ?? self::DEFAULT_AWS_EC2_METADATA_V1_DISABLED;
@@ -369,7 +373,7 @@ private function resolveEndpoint(): string
                 self::CFG_EC2_METADATA_SERVICE_ENDPOINT,
                 $this->getDefaultEndpoint(),
                 'string',
-                ['use_aws_shared_config_files' => true]
+                ['use_aws_shared_config_files' => $this->useAwsSharedConfigFiles]
             );
         }
 
@@ -420,7 +424,7 @@ private function resolveEndpointMode(): string
                 self::CFG_EC2_METADATA_SERVICE_ENDPOINT_MODE,
                     self::ENDPOINT_MODE_IPv4,
                 'string',
-                ['use_aws_shared_config_files' => true]
+                ['use_aws_shared_config_files' => $this->useAwsSharedConfigFiles]
             );
         }