Refactor `clear()` to help the user to avoid `ClearData`

[gfx-rs]

Refactor `clear()` to help the user to avoid `ClearData`

[kvark]

My main concern here is that a method call like that: list.clear(None, Some(1.0), None) is by far not self-descriptive. And if we introduce a separate time for each like that: list.clear(gfx::NoClearColor, gfx::ClearDepth(1.0), gfx::NoClearStencil), then there is no ergonomic benefit over what we already have now...

[brendanzab]

Perhaps:

list.with_color([0.3, 0.3, 0.3, 1.0])
    .with_depth(1.0)
    .clear(&frame);

list.clear(data, &frame);

[kvark]

Sounds good, especially since it can be implemented on top of the existing clear(), and self-contained within the front-end interface.

[brendanzab]

We will need to document this nicely. Assigned it to myself.

[kvark]

Keep in mind that this may be slightly inconsistent with other list calls. I.e. draw() doesn't have any builder, nor that It'd be useful. In the future, we are gonna have the transform() call, which would probably not need a builder either. So the clearing is gonna stand out a little.

[brendanzab]

Hmm. We need to think of a clean, unified way of doing all of this :/

[kvark]

@bvssvni proposed .clear_color_depth(color, depth)

[kvark]

Closing in favor of #630