Currently, the cbor package supports go1.17 but that requires supporting additional code because cbor uses features added by go1.20.

We can reduce maintenance, testing, and (private) fuzzing burden by dropping support for Go versions older than 1.20.

While at it, replace some deprecated Go syntax:

• interface{} ➡ any
• reflect.Ptr ➡ reflect.Pointer
• reflect.PtrTo ➡ reflect.PointerTo