Add the SimpleScalarSanitizer class

The `SimpleScalarSanitizer` class represents common scalar types which
cannot realistically carry taint (e.g. primitives/numbers, and
eventually UUIDs and Dates)

java/ql/lib/semmle/code/java/security/dataflow/CommonSanitizers.qll

@@ -0,0 +1,15 @@
+/** Classes to represent sanitizers commonly used in dataflow and taint tracking configurations. */
+
+import java
+import semmle.code.java.dataflow.DataFlow
+
+/**
+ * A node whose type is a common scalar type, such as primitives or their boxed counterparts.
+ */
+class SimpleScalarSanitizer extends DataFlow::Node {
+  SimpleScalarSanitizer() {
+    this.getType() instanceof PrimitiveType or
+    this.getType() instanceof BoxedType or
+    this.getType() instanceof NumberType
+  }
+}