Prepass normals lack precision

## Bevy version [a879f98](https://github.com/bevyengine/bevy/commit/a879f98d3b757fe19afb17b976b11f49119ab900)

The prepass normals appear to lack precision. Not sure if it's a limitation of the [prepass normals format](https://github.com/bevyengine/bevy/blob/main/crates/bevy_core_pipeline/src/prepass/mod.rs#L42), or something else.

This is a helpful paper regarding formats for normals: https://jcgt.org/published/0003/02/01/paper.pdf
Unfortunately, it doesn't have an image of RGB10A2, but in a table it does list snorm10×3, which may be similar.

[Test scene](https://gist.github.com/DGriffin91/502ab6b6baa3e2cfff3e85b85ae1019d) for images below. [Version for testing](https://gist.github.com/DGriffin91/232da7eca8cf819c1478cb3053cd5079) with [Deferred Rendering PR](https://github.com/bevyengine/bevy/pull/9258).

Normals without prepass:

Normals with prepass:

Normals using oct24 format from [Deferred Rendering PR](https://github.com/bevyengine/bevy/pull/9258)