More flexible date ranges for Trend Metrics

[alies-dev]

\Laravel\Nova\Metrics\Trend::aggregate method has lines:

$startingDate = $this->getAggregateStartingDate($request, $unit, $timezone),
$endingDate = CarbonImmutable::now($timezone),

it will be nice to extract CarbonImmutable::now($timezone) into another protected method, similar to getAggregateStartingDate, so developers can override it for customisation purposes (I have to display trends for whole years, like 2023, 2022, etc, and do not end them by today's date).

[crynobone]

Released with Laravel Nova 5.0.0

Feel free to open up a new issue if you're still experiencing this problem on the latest version.