MDL-59057 analytics: Get rid of week_before_course_start

It is useless at site level. It can be useful at course level but
I removed it in favour of single_range + is_valid_*

Part of MDL-57791 epic.

analytics/classes/local/time_splitting/week_before_course_start.php

@@ -1,57 +0,0 @@
-<?php
-// This file is part of Moodle - http://moodle.org/
-//
-// Moodle is free software: you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// Moodle is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-// GNU General Public License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
-
-/**
- * One week before the course start.
- *
- * @package   core_analytics
- * @copyright 2016 David Monllao {@link http://www.davidmonllao.com}
- * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
- */
-
-namespace core_analytics\local\time_splitting;
-
-defined('MOODLE_INTERNAL') || die();
-
-class week_before_course_start extends base {
-
-    public function get_name() {
-        return get_string('timesplitting:weekbeforecoursestart', 'analytics');
-    }
-
-    public function is_valid_analysable(\core_analytics\analysable $analysable) {
-        if ($analysable instanceof \core_analytics\site) {
-            // Defer checking to is_valid_sample.
-            return true;
-        }
-        if ($analysable instanceof \core_analytics\course && !$analysable->get_start()) {
-            return get_string('nocoursestart', 'analytics');
-        }
-
-        // Default to true.
-        return true;
-    }
-
-    protected function define_ranges() {
-        return [
-            [
-                'start' => 0,
-                'end' => \core_analytics\analysable::MAX_TIME,
-                'time' => $this->analysable->get_start() - WEEKSECS
-            ]
-        ];
-    }
-}