✨ (concepts) Add new concept exercise `phone-number-analysis`

[devkabiir]

This is inspired by the same in csharp track. Provides a gentle introduction to tuples.

[senekor]

The author of this PR has stopped responding in the discussions planning the work on the syllabus. But there's been work put into reviews already, so I'm keeping it open in case it can be salvaged in a future attempt to create a good syllabus.