[Coroutines][LazyCallGraph] addSplitRefRecursiveFunctions allows spurious ref edges between new functions. (#116285)
The addSplitRefRecursiveFunctions LazyCallGraph helper should not
require a reference between every new function. Spurious ref edges
between the new functions are allowed and the new function are
considered to be a RefSCC. This change clarifies that this is the case
in the method's description and its DEBUG mode verifier.