New rule to introduce safe recursive call as a variable
New rule to introduce safe recursive call as a variable

Remove SafeRecursiveCalls from Grammars.default
IntroduceRecCalls keeps only examples that lead to no 'choose'
IntroduceRecCalls is normalizing
Make 1 benchmark tougher

epfl-lara/stainless,epfl-lara/stainless,epfl-lara/stainless,epfl-lara/stainless