Convert while-pop_front loops to iterator loops

[YYF233333]

Cleanup loops which are linear scan but use while.

Semantically, this change provides greater optimization potential because we can now batch free elements. However, this benefit can only be realized after switching the container to Vector/LocalVector, as List always removes elements one by one.

Some loops are at the bottom of their scope and the container destruct right after the loop, I omit clear() for them.

[bruvzg]

godot/core/templates/list.h

Lines 467 to 471 in 1f56d96

	void clear() {
	while (front()) {
	erase(front());
	}
	}

For List this will just add another unnecessary loop, which might be optimized out by compiler, but definitely need performance testing.

[Ivorforce]

godot/core/templates/list.h

Lines 467 to 471 in 1f56d96

	void clear() {
	while (front()) {
	erase(front());
	}
	}

For List this will just add another unnecessary loop, which might be optimized out by compiler, but definitely need performance testing.

I don't think the compiler can optimize this out, as it would violate code execution order.
With lists, it probably is faster to do a while - pop_front than iteration.
In rust, this would be conveniently solved with a into_iterator(), but I don't think there's a clean way to do this in C++.

[YYF233333]

I update the "other half" of this PR which replace these List with LocalVector. Now it is 2 iteration + 1 memfree v.s. 1 iteration + N memfree, and I can say generally this will be faster.