:feat: adds option to update the events.

[PRBaraiya]

Description

This PR adds a new method in EventController named update to update the existing event with the updated one.

This PR also adds some code cleanups in EventController which include,

• Moves events-specific operations like, add, delete, and update in the CalendarData class.
• Refactor logic in methods for event manipulation and event fetch.
• Adds new parameter includeFullDayEvents in getEventsOnDay to decide whether to include full-day events in the returned list or not.
• Adds getters isRangingEvent and isFullDayEvent in CalendarEventData to check if the event is a ranging event or a full-day event.
• Adds new method occursOnDate in CalendarEventData to check if the event occurs on the given date or not.
• Use the includeFullDayEvents flag while getting events for week and day view to avoid unnecessary calculations.

Checklist

• The title of my PR starts with a [Conventional Commit] prefix (fix:, feat:, docs: etc).
• I have followed the [Contributor Guide] when preparing my PR.
• I have updated/added tests for ALL new/updated/fixed functionality.
• I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• I have updated/added relevant examples in examples or docs.

Breaking Change?

• Yes, this PR is a breaking change.
• No, this PR is not a breaking change.

Related Issues

Closes issue #125