Build/Test Tools: Disable process timeout when running PHPUnit tests via Composer.

When running the full test suite locally via `npm run grunt phpunit` or `composer test`, it is not uncommon for the test run to exceed the Composer's default timeout, causing an error in the middle of the test output:
{{{
The process "..." exceeded the timeout of 300 seconds.
}}}

This commit disables the process timeout for the `composer test` command, allowing the test run to complete successfully.

Follow-up to [47881], [51016].

Props ironprogrammer, robinwpdeveloper, SergeyBiryukov.
Fixes #55919.

git-svn-id: https://develop.svn.wordpress.org/trunk@54355 602fd350-edb4-49c9-b593-d223f7449a82

composer.json

@@ -29,6 +29,6 @@
 		"format": "@php ./vendor/squizlabs/php_codesniffer/bin/phpcbf --report=summary,source",
 		"lint": "@php ./vendor/squizlabs/php_codesniffer/bin/phpcs --report=summary,source",
 		"lint:errors": "@lint -n",
-		"test": "@php ./vendor/phpunit/phpunit/phpunit"
+		"test": [ "Composer\\Config::disableProcessTimeout", "@php ./vendor/phpunit/phpunit/phpunit" ]
 	}
 }