Change repeat syntax and add range repeats

[diondokter]

Repeats are now:

• Count: [3::2]
  • Len = 3
  • Stride = 2
• Range: [3:1:2]
  • End = 3 (inclusive)
  • Start = 1
  • Len = 3
  • Stride = 2
• Enum: [Foo:2]
  • Stride = 2

But!
The meaning of number 3 changes from exclusive in the count scenario and inclusive in the range scenario. Not sure about that.
But making the count be inclusive feels super wrong since it's such a strong convention in languages to specify arrays with the len, not the last index.

While the order of start and end are different, the range syntax here is inspired by python (and matches the field address range expression).