Retrieve cron jobs ready to be run.

Returns the results of _get_cron_array() limited to events ready to be run,
ie, with a timestamp in the past.

function wp_get_ready_cron_jobs() {
	/**
	 * Filter to preflight or hijack retrieving ready cron jobs.
	 *
	 * Returning an array will short-circuit the normal retrieval of ready
	 * cron jobs, causing the function to return the filtered value instead.
	 *
	 * @since 5.1.0
	 *
	 * @param null|array[] $pre Array of ready cron tasks to return instead. Default null
	 *                          to continue using results from _get_cron_array().
	 */
	$pre = apply_filters( 'pre_get_ready_cron_jobs', null );

	if ( null !== $pre ) {
		return $pre;
	}

	$crons    = _get_cron_array();
	$gmt_time = microtime( true );
	$results  = array();

	foreach ( $crons as $timestamp => $cronhooks ) {
		if ( $timestamp > $gmt_time ) {
			break;
		}

		$results[ $timestamp ] = $cronhooks;
	}

	return $results;
}