cranelift: Implement float rounding operations (#4397)

Implements the following operations on the interpreter:
* `ceil`
* `floor`
* `nearest`
* `trunc`

cranelift/interpreter/src/step.rs

@@ -728,10 +728,10 @@ where
             (a, b) if a.is_zero()? && b.is_zero()? => a,
             (a, b) => a.max(b)?,
         }),
-        Opcode::Ceil => unimplemented!("Ceil"),
-        Opcode::Floor => unimplemented!("Floor"),
-        Opcode::Trunc => unimplemented!("Trunc"),
-        Opcode::Nearest => unimplemented!("Nearest"),
+        Opcode::Ceil => assign(Value::ceil(arg(0)?)?),
+        Opcode::Floor => assign(Value::floor(arg(0)?)?),
+        Opcode::Trunc => assign(Value::trunc(arg(0)?)?),
+        Opcode::Nearest => assign(Value::nearest(arg(0)?)?),
         Opcode::IsNull => unimplemented!("IsNull"),
         Opcode::IsInvalid => unimplemented!("IsInvalid"),
         Opcode::Trueif => choose(