External Libraries: Update the Requests library to version 2.0.0.

This is a major release and contains breaking changes.

Most important changes to be aware of for this release:
* All code is now namespaced. Though there is a full backward compatibility layer available and the old class names are still supported, using them will generate a deprecation notice (which can be silenced by plugins if they'd need to support multiple WP versions). See the [https://requests.ryanmccue.info/docs/upgrading.html upgrade guide] for more details.
* A lot of classes have been marked `final`. This should generally not affect userland code as care has been taken to not apply the `final` keyword to classes which are known to be extended in userland code.
* Extensive input validation has been added to Requests. When Requests is used as documented though, this will be unnoticable.
* A new `WpOrg\Requests\Requests::has_capabilities()` method has been introduced which can be used to address #37708.
* A new `WpOrg\Requests\Response::decode_body()` method has been introduced which may be usable to simplify some of the WP native wrapper code.
* Remaining PHP 8.0 compatibility fixed (support for named parameters).
* PHP 8.1 compatibility.

Release notes: https://github.com/WordPress/Requests/releases/tag/v2.0.0

For a full list of changes in this update, see the Requests GitHub:
https://github.com/WordPress/Requests/compare/v1.8.1...v2.0.0

Follow-up to [50842], [51078].

Props jrf, schlessera, datagutten, wojsmol, dd32, dustinrue, soulseekah, costdev, szepeviktor.
Fixes #54504.

git-svn-id: https://develop.svn.wordpress.org/trunk@52244 602fd350-edb4-49c9-b593-d223f7449a82

tests/phpunit/tests/widgets/wpWidgetRss.php

@@ -106,7 +106,7 @@ class Tests_Widgets_wpWidgetRss extends WP_UnitTestCase {
 		);
 
 		return array(
-			'headers'  => new Requests_Utility_CaseInsensitiveDictionary( $single_value_headers ),
+			'headers'  => new WpOrg\Requests\Utility\CaseInsensitiveDictionary( $single_value_headers ),
 			'body'     => file_get_contents( DIR_TESTDATA . '/feed/wordpress-org-news.xml' ),
 			'response' => array(
 				'code'    => 200,