We are now using the `session-data` method of the Beacon API to send
site information to HelpScout
(https://developer.helpscout.com/beacon-2/web/javascript-api/#beacon-session-data).
This method has a limit of 20 attribute-value pairs and since we had
more, it was necessary to combinte a few values under the same
attribute.
[MAILPOET-4525]
This commit adds a new flag to \MailPoet\Helpscout\Beacon::getData() to
mask half of the API key when this method is used to get information for
the System Info page. When it is used to pass information to HelpScout
nothing should change and the full key will be returned.
[MAILPOET-4009]
