f64 depth images aren't displayed in the UI

[nikolausWest]

After #608 f64 depth images don't get shown in the viewer. Instead we get the following on logs in the terminal:

2022-12-23T12:22:46.423032Z  WARN re_viewer::misc::caches::tensor_image_cache: Bad image "tensor [270, 480]": Don't know how to turn a tensor of shape=[270, 480] and dtype=F64 into an image

[jleibs]

This doesn't just apply to depth images but to any f64 monochrome image.

[teh-cmc]

This applies to any image shaped tensors, whether it's depth or albedo.

ClassicTensor::as_dynamic_image doesn't handle f64s at all.

Also very related to #1435 and #1436

[emilk]

Closed by https://github.com/rerun-io/rerun/pull/1686