Naga fails to translate certain correct SPIR-V

[Shfty]

Some valid rust-gpu code - such as the idiomatic for i in 0..10 loop sytax, or reading from a depth texture - is not yet supported by naga, or is subject to naga-internal bugs, thus preventing it from being used with bevy.

This can be worked around in the interim by using SPIR-V passthrough, but this is not yet supported by bevy.

A PR exists at bevy/3996, but was closed by its author before being merged. This code still works, and was deemed desirable by the bevy team, so I'll look at adopting said PR and getting it merged.

[Shfty]

Opened a new PR: bevy/8131