Java: use AccessPathSyntax.qll to parse input/output summary specs

javascript/ql/lib/semmle/javascript/frameworks/data/internal/AccessPathSyntax.qll

@@ -47,6 +47,9 @@ class AccessPath extends string instanceof AccessPath::Range {
     result = count(int n | exists(this.getRawToken(n))) and
     not hasSyntaxError()
   }
+
+  /** Gets the `n`th-last token, with 0 being the last token. */
+  AccessPathToken getLastToken(int n) { result = getToken(getNumToken() - 1 - n) }
 }
 
 /**