Add test for mesh transformations

[greeble-dev]

Objective

Add a test that will repro issues with mesh transformations, like #17992.

Solution

The test transforms a mesh in three different ways. Each transformation should have the same visual result.

The screenshot shows the test reproducing #17992. Mesh 1 should have matched mesh 2 and 3.

Problems

Right now the test is not suitable for screenshot comparison - the light is animated.

Testing

Tested on Win10/Vulkan/Nvidia.

cargo run --example transform_mesh --features "pbr_anisotropy_texture"

[greeble-dev]

CI failure appears unrelated to the PR.

https://github.com/bevyengine/bevy/actions/runs/13727867039/job/38398331235?pr=18194#logs

Run cargo deny check advisories
error[unmaintained]: paste - no longer maintained
    ┌─ /home/runner/work/bevy/bevy/Cargo.lock:369:1
    │
369 │ paste 1.0.15 registry+https://github.com/rust-lang/crates.io-index
    │ ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ unmaintained advisory detected
    │
    ├ ID: RUSTSEC-2024-0436
    ├ Advisory: https://rustsec.org/advisories/RUSTSEC-2024-0436

[mockersf]

rather than using anisotropy, didn't we use to have a debug view to show tangents/normals?

[greeble-dev]

The shader_prepass example shows normals, but I couldn't find anything that shows tangents. Although a TangentPrepass might be a valid (if somewhat niche) feature?

I also considered drawing a per-vertex gizmo. But that doesn't cover the third test case which validates transforms in the shader.

So my guess is that anisotropy is the least worst choice right now.

[greeble-dev]

I think that requiring feature pbr_anisotropy_texture is either a bug in the shader or the documentation. The example doesn't actually use anisotropy textures, but if I disable them then anisotropy doesn't work at all.

I'll file that as a bug if this PR goes through.