Module settings are updated and re-organized

Version 3.x introduced support for rate limiting of non-crawlers and support for multiple backends. These new features required settings array to be re-organized and expanded.

Settings that were renamed and/or moved:
$settings['operations'] is now $settings['bot_traffic']['requests']
$settings['interval'] is now $settings['bot_traffic']['interval']

Settings that were added in new version:
Required:
$settings['backend']
Optional:
$settings['regular_traffic']['requests']
$settings['regular_traffic']['interval']

BEFORE the change (version 1.0 and version 2.0)

$settings['crawler_rate_limit.settings']['enabled'] = TRUE;
$settings['crawler_rate_limit.settings']['operations'] = 100;
$settings['crawler_rate_limit.settings']['interval'] = 600;

AFTER the change (version 3.0)

$settings['crawler_rate_limit.settings']['enabled'] = TRUE;
$settings['crawler_rate_limit.settings']['backend'] = 'redis';
$settings['crawler_rate_limit.settings']['bot_traffic'] = [
  'requests' => 100,
  'interval' => 600,
];
// Optionally, add settings for rate limiting regular traffic.
$settings['crawler_rate_limit.settings']['regular_traffic'] = [
  'requests' => 400,
  'interval' => 720,
];