[shaders][msl] Enable zero_initialize_workgroup_memory setting

Zero-initializing workgroup memory works around a Metal driver bug
that can cause the tile_alloc and coarse stages to freeze up the system
when running natively on Metal due to their use of `workgroupUniformLoad`.
See gfx-rs/naga#2482 for more details about this bug.

Zero-initializing workgroup memory also makes the native Metal shaders
match the behavior of the current wgpu runner and the invariants of the
original WGSL that the shaders were authored in.

crates/shaders/src/compile/msl.rs

@@ -43,7 +43,7 @@ pub fn translate(shader: &ShaderInfo) -> Result<String, naga_msl::Error> {
         spirv_cross_compatibility: false,
         fake_missing_bindings: false,
         bounds_check_policies: naga::proc::BoundsCheckPolicies::default(),
-        zero_initialize_workgroup_memory: false,
+        zero_initialize_workgroup_memory: true,
     };
     let (source, _) = naga_msl::write_string(
         &shader.module,