Fix a problem in the codebase where we create, schedule and update newsletters in the user time zone, but we set the ProcessedAt with another timezone
Also, `Carbon::createFromTimestamp($this->wp->currentTime('mysql'))` is not a valid date.
It would return date: '1970-01-01 00:35:29.000000'
MAILPOET-5795
We can't create mailer directly in DI container using the factory because it may fail in case
the plugin is not configured properly and prevent plugin from start.
The Mailer was previously injected because it contains lazy initialization.
The lazy initialization in the singleton Mailer service was dangerous,
because when used with some custom parameters it could cause that all services
that inject the Mailer from DI would use the custom config instead the default.
[MAILPOET-4115]
This commit makes some changes to the stats email. It displays just the
clicked stats in the first row and it moves the opened stats to the
second row. It also adds machine-opens alongside opens in the second
row.
[MAILPOET-3324]
