Add Sequence.split(maxLength:)

[CTMacUser (Daryle Walker)]

This is a "chunked sequence," which has been brought up before:

• What makes a good lazy procedure? And how to do it?
• Add an adjacentPairs algorithm to Sequence
• Supporting collection slice by slices of a given size parameter
• Pre-pitch: striding through collections should be easier
• Chunking Collections and Strings in Swift 5.1