Finalize Swift generation support

[baywet]

related microsoft/kiota#1444

With swift work started, we need to finish the generation work:

• implement the whole of CodeMethodWriter
• unit tests for all the writers
• other date types support (DateTimeOffset, Time, Duration)
• parse method for enums?
• accessors for model properties?

For reference, the file names contain a has to workaround this issue, this might need to be reviewed.