feat(const_eval): impl. saturate

CHANGELOG.md

@@ -45,6 +45,7 @@ Bottom level categories:
     - [#4879](https://github.com/gfx-rs/wgpu/pull/4879) by @ErichDonGubler:
         - `abs`
         - `round`
+        - `saturate`
 
 ## v0.19.0 (2024-01-17)
 

naga/src/proc/constant_evaluator.rs

@@ -847,6 +847,9 @@ impl<'a> ConstantEvaluator<'a> {
                     Float::F32([e]) => Ok(Float::F32([(round_ties_even(e as f64) as f32)])),
                 })
             }
+            crate::MathFunction::Saturate => {
+                component_wise_float!(self, span, [arg], |e| { Ok([e.clamp(0., 1.)]) })
+            }
             fun => Err(ConstantEvaluatorError::NotImplemented(format!(
                 "{fun:?} built-in function"
             ))),