JS: Cache StandardEndpointFilters::isNumeric

This predicate operates on a large set of starting nodes.
Caching it is easier than attempting to optimise the helper
predicate `isReadFrom` without slowing down other more
specialised callers of the helper predicate.

Author: adityasharad

javascript/ql/experimental/adaptivethreatmodeling/lib/experimental/adaptivethreatmodeling/StandardEndpointFilters.qll

@@ -53,6 +53,9 @@ predicate isSomeModeledArgument(DataFlow::Node n) {
 /**
  * Holds if `n` appears to be a numeric value.
  */
+// Performance optimisation: This predicate operates on a large set of
+// starting nodes, so compute it only once and cache it.
+cached
 predicate isNumeric(DataFlow::Node n) { isReadFrom(n, ".*index.*") }
 
 /**