Implement deep copy methods for components

[axunonb]

• Implemented and completed CopyFrom method from ICopyable interface in multiple classes for deep copying.
• Removed questions in code and implemented solution
• Updated ICopyable interface documentation.
• Introduced pattern matching for better readability
• Added new test methods in CopyComponentTests class for deep copying various calendar components.
• Fixed broken SerializationTests.AttendeesSerialized() (Corrected attendee names and fixed typos in assertions.)
• Refactored CalendarObjectBase (should eventually become abstract)
• Added ExcludeFromCodeCoverage attribute to CalendarObjectList.
• Updated Ical.Net.csproj to latest C# version.

Fixes #149

[axunonb]

@minichma

#149 focuses on a special case where deep copy did not work, It would have been simple to fix.
This PR is an effort for a generic approach to make ICopyable.Copy() work for all components.

Not sure, whether I discovered all components where an individual CopyFrom is needed.
The implementation of the ICopyable interface is a bit tricky: If CopyFrom is not overridden in a component, it falls back to parents' implementation. That, however, may or may not copy all members.
At the same time T Copy<T>() is only implemented in the base class CalendarDataType. From here, all the calls to CopyFrom are invoked.

Any comments and further hints are welcome.

[minichma]

@axunonb I will try to find some time for a review, but this could take a few days.

[axunonb]

Yes, of course, the task required more changes than I expected due to incomplete implementation.
EXDATE looks like another hotspot (#614 #590 #591) to be fixed

[minichma]

LGTM, just minor comments.

The following classes don't have CopyFrom methods, because they are expected to have all their data stored in the Properties collection. Did only a very rough check to verify, this actually is the case.

Ical.Net.Calendar
Ical.Net.VTimeZoneInfo
Ical.Net.DataTypes.EncodableDataType
Ical.Net.CalendarComponents.Alarm
Ical.Net.CalendarComponents.CalendarEvent
Ical.Net.CalendarComponents.FreeBusy
Ical.Net.CalendarComponents.Journal
Ical.Net.CalendarComponents.RecurringComponent
Ical.Net.CalendarComponents.Todo
Ical.Net.CalendarComponents.UniqueComponent
Ical.Net.CalendarComponents.VTimeZone
Ical.Net.CalendarComponents.VTimeZone.IntervalRecurrencePattern

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud