Packaging: Rafactor Javascript core libraries

Extract the external facing `qll` files into the codeql/javascript-all
query pack.

javascript/ql/lib/semmle/javascript/Unit.qll

@@ -0,0 +1,10 @@
+/** Provides the `Unit` class. */
+
+/** The unit type. */
+private newtype TUnit = TMkUnit()
+
+/** The trivial type with a single element. */
+class Unit extends TUnit {
+  /** Gets a textual representation of this element. */
+  string toString() { result = "Unit" }
+}