Fix PHP 8.2 deprecation warnings (#165)

* Fix PHP 8.2 deprication warnings

This fixes the following warnings:

 8192: Creation of dynamic property WP_CLI\Tests\Context\FeatureContext::$result is deprecated in /wp-cli-tests/src/Context/WhenStepDefinitions.php line 39

8192: Creation of dynamic property WP_CLI\Tests\Context\FeatureContext::$email_sends is deprecated in /wp-cli-dev/wp-cli-tests/src/Context/WhenStepDefinitions.php line 40

Which cause behat tests to fail with PHP 8.2

* Add code comments for these variables

---------

Co-authored-by: Daniel Bachhuber <daniel.bachhuber@automattic.com>

src/Context/FeatureContext.php

@@ -21,6 +21,16 @@ class FeatureContext implements SnippetAcceptingContext {
 	use ThenStepDefinitions;
 	use WhenStepDefinitions;
 
+	/**
+	 * The result of the last command run with `When I run` or `When I try`. Lives until the end of the scenario.
+	 */
+	private $result;
+
+	/**
+	 * The number of emails sent by the last command run with `When I run` or `When I try`. Lives until the end of the scenario.
+	 */
+	private $email_sends;
+
 	/**
 	 * The current working directory for scenarios that have a "Given a WP installation" or "Given an empty directory" step. Variable RUN_DIR. Lives until the end of the scenario.
 	 */