Fix deferred rendering (#15656)

# Objective

Fixes #15525

The deferred and mesh pipelines tonemapping LUT bindings were
accidentally out of sync, breaking deferred rendering.

As noted in the issue it's still broken on wasm due to hitting a texture
limit.

## Solution

Add constants for these instead of hardcoding them.

## Testing

Test with `cargo run --example deferred_rendering` and see it works, run
the same on main and see it crash.