Is your feature request related to a problem? Please describe.
Min/Max sampler filter modes have widespread support in native APIs and are useful to reduce bandwidth requirements of a set of image processing operations, like building a mipmap chain for the depth buffer.

Describe the solution you'd like
Add an optional feature SAMPLER_FILTER_MINMAX as well as "Min" and "Max" variants

If the hello_triangle example is changed slightly to only draw the triangle once, and we change the color attachment's load_op to wgpu::LoadOp::Load instead of Clear, my expectation is that the result is the same, except that the green clear color is gone. However the result is that the red triangle only shows up every other frame, with blank frames in between.

Is this expected behavi