Build/Test Tools: Introduce support for a `WP_TESTS_CONFIG_FILE_PATH` constant to override the test suite config file location.

This can be used in phpunit.xml:

{{{
<php>
	<const name="WP_TESTS_CONFIG_FILE_PATH" value="/path/to/wp-tests-config.php" />
</php>
}}}

Props clarinetlord

Fixes #39734

Built from https://develop.svn.wordpress.org/trunk@43369


git-svn-id: http://core.svn.wordpress.org/trunk@43197 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.0-alpha-43367';
+$wp_version = '5.0-alpha-43369';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.