Remove source and test files related to RDATE/EXDATEcollections

Remove solution for RDATE/ESDATE introduced earlier in this PE

The commit removes several test and source files related to period and exception date collections in calendar events. Specifically, the following files have been completely removed:
- `PeriodCollectionBase.cs`
- `ExceptionDateCollection.cs`
- `RecurrencePeriodCollection.cs`
- `PeriodCollectionTests.cs`
- `RecurrenceWithExDateTests.cs`
- `RecurrenceWithRDateTests.cs`

Author: axunonb