Enhance new calendar widget

The current calendar widget that supports multiple meetings per day is not in its final state.

Once we get started with the new Scheduling Tool UI/UX, we should improve this widget experience.
UX calendar discussion is documented in [this Figma file](https://www.figma.com/file/OdYeiVYd0PYK8qC5FnsNMU/Multiple-meetings-per-day-in-Scheduling-Tool?type=whiteboard&node-id=0%3A1&t=YiYIGY4wmuFmVbHV-1).

And some things we can done to improve the current implementation are:

- [ ] Use the vertical calendar instead of the horizontal one
- [ ] Add "Current selected time", "Notes", and "Schedule for..." messages inside the calendar, or at least make them match the same style.

Start by reviewing the linked Figma file and the current calendar widget implementation to confirm the intended Scheduling Tool UI/UX. Done means adopting the vertical calendar and making the “Current selected time,” “Notes,” and “Schedule for...” messages appear inside it or match its style.

Written by the indexing model from the issue text.