Use is_wasm_parameter in translating wasm calls (#1352)

* Use `is_wasm_parameter` in translating wasm calls

Added in #1329 it's now possible for multiple parameters to be non-wasm
parameters, so the previous `param_types` method is no longer suitable
for acquiring all wasm-related parameters, rather then `FuncEnvironment`
must be consulted. This removes usage of `param_types()` as a method
from the wasm translation and instead adds a custom method inline for
filtering the parameters based on `is_wasm_parameter`.

* Apply feedback

* Run rustfmt

* Don't require `mut`

* Run rustfmt

cranelift/codegen/src/ir/extfunc.rs

@@ -102,24 +102,6 @@ impl Signature {
             .count()
             > 1
     }
-
-    /// Collect the normal parameter types of the signature; see `[ArgumentPurpose::Normal]`.
-    pub fn param_types(&self) -> Vec<Type> {
-        self.params
-            .iter()
-            .filter(|ap| ap.purpose == ArgumentPurpose::Normal)
-            .map(|ap| ap.value_type)
-            .collect()
-    }
-
-    /// Collect the normal return types of the signature; see `[ArgumentPurpose::Normal]`.
-    pub fn return_types(&self) -> Vec<Type> {
-        self.returns
-            .iter()
-            .filter(|ap| ap.purpose == ArgumentPurpose::Normal)
-            .map(|ap| ap.value_type)
-            .collect()
-    }
 }
 
 /// Wrapper type capable of displaying a `Signature` with correct register names.