In one of my personal projects I stumbled across a case where I wanted
to be cautious with the change detection while also not sacraficing any
performance.

My use case: I basically have a horizontal surface which is saved as a
collection of `Vec<Vec2>` in a component. The component also includes a
height field. Now when the height is updated there only have two (three)
options:

- The collection of points can be cloned so the existing `set_if_neq` is
  usable
- The `set_if_neq` code can be inlined and adjusted for this special case
- (The component can be split up into two more granular components)

I have to acknowledge that the third point here is probably the way to
go in most cases, but I was curious:

- if it would be possible to have a more flexible API and how that would
  look like
- if you are interested in this change in general

No hard feelings if we just end up rejecting this PR. I'm also totally
fine with this. But maybe it's useful to anyone and I just wanted to
hear your feedback first before tossing this back into the void and
forgetting about it.

This reverts commit 71b90f5.

…_neq`