[PIWOO-363] Feature flag for Merchant capture module

[inpsyde-maticluznar]

The module is completely isolated from the rest of the code. To achieve that, I had to apply filters to advanced settings array inc/settings/mollie_advanced_settings.php.

Filter is called: inpsyde.mollie-advanced-settings
It sends two parameters: settings & pluginName

Starter point of the MerchantCaptureModule was moved inside init hook. It was done, because we want to filter the flag value outside of the plugin.

To enable MerchantCaptureModule, you have to use the following filter:
add_filter('mollie_wc_gateway_enable_merchant_capture_module', '__return_true');