staticcheck: Fix unused fields

The embedded `nocmp` field and other similar fields are unused in tests
and the rest of our code.

We can get the effect of `nocmp` without embedding the fields by using
`_ nocmp` as a field.

bool.go

@@ -28,7 +28,7 @@ import (
 
 // Bool is an atomic type-safe wrapper for bool values.
 type Bool struct {
-	nocmp // disallow non-atomic comparison
+	_ nocmp // disallow non-atomic comparison
 
 	v Uint32
 }