Datetime picker

#### Is your feature request related to a problem? Please describe

I'd like users to specify a time range by defining two datetimes. The beginning of the time range cannot lie in the past and the end (obviously) must be later than the beginning. Currently, if a minimum time for the time picker is specified this limits the time for all days even those in the future that would specify a valid end time.

#### Describe the solution you'd like

Currently, separate date and time pickers are available. A combined datetime picker has been suggested before here: https://github.com/h2oai/wave/issues/1537. My motivation for the request is different then for that issue which is why I created a new one.

I'd like either a combined datetime picker that takes a min and max limit as datetime. Alternatively, my problem would be solved if the time picker takes a datetime or timestamp as limit (but that does not seem like a good solution).

#### Describe alternatives you've considered

The alternative for my use case would be to remove min/max limiters and add a validation step that prevents form submission for invalid start/stop inputs. But UI limitation would be easier to use.

#### Additional context

None