[REF] web: refactor the calendar view

Improve design and introducing several usability improvements:
- Removed customization of an event card, just display event title.
- Added popover, popover consist of two sections:
    1) Show the title, date and time of an event. Date and time are
       automatically computed according to the user timing preferences,
       language and event duration. Can be hidden with hide_date/hide_time
       attribute respectively.
    2) Display all the fields specified inside the <calendar/> element.
       fields can be specified with a widget and its options.
       e.g. <field name="name" string="Custom Name" widget="char" options="{}"/>
- Show avatar in popover for filters.
- Removed hide sidebar feature.
- Increase readability using a better color selection.
- Better UI in mobile.

And, Adapted test cases

Task 1919926

Co-authored-by: jat-odoo <jat@openerp.com>