Range mutator

[richardwerkman]

Is your feature request related to a problem? Please describe.
Range operator expressions are not mutated at the moment. Even though this contains crucial logic sometimes.

Describe the solution you'd like

Original	Mutated
..	0
..end	..
..3	..2
..3	..4
start..	..
2..	1..
2..	3..
start..end	..
2..2	1..2
2..2	3..2
2..2	2..1
2..2	2..3
^start..	..
^2..	^1..
^2..	^3..
..^end	..
..^2	..^1
..^2	..^3
start..^end	..
2..^2	1..^2
2..^2	3..^2
2..^2	2..^1
2..^2	2..^3
^start..^end	..
^2..^2	^3..^2
^2..^2	^2..^1

So basically always replace with .. and if the start or end value is a declared value, increase this by one and decrease by one (check for bounds).

Additional context
See: https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/operators/member-access-operators#range-operator-

[rouke-broersma]

Not sure we should implement the edge increase/decrease mutations, we don't do this for any other mutator either.

[richardwerkman]

We could also add/remove the ^? Would that make more sense?

[dupdob]

I do not think removing the 'relative to end' marker would create more interesting mutation than increment/decrement.
On an implementation note, while the mutation seems simple to generate, controlling them will be a bit more difficult: I am not sure we can use a ternary operator with a range expression.
but it should be a matter of adding a range expression orchestrator then