Switch time inputs to input[type="time"]

[fmartingr]

The create event modal uses simple <select/> elements to select the time of the event. <input/> elements can be of type time which will leave the implementation to the browser with an already defined UI and they also allow for a min/max/step parameters to customize the options.

Acceptance criteria

• Migrate custom selects to input[type="time"]
• Do not break current integration with the date field:
  • If the date is today, we should only allow a start/end time after the current time.
  • End time should only allow times after Start time.

Related tasks

• Allow creation of calendar events that span multiple days mattermost-plugin-mscalendar#323