FillForward overloads without a fillSelector are not optimals

[Orace]

We should avoid branching in loops when possibles

MoreLINQ/MoreLinq/FillForward.cs

Lines 111 to 120 in c3516e3

	foreach (var item in source)
	{
	if (predicate(item))
	{
	yield return seeded
	? fillSelector != null
	? fillSelector(item, seed)
	: seed
	: item;
	}