JS: Simplify aggregation of tokens into entity strings

Change the cutoff logic from `count` to `strictcount`, since we know it only applies
to a non-empty set of results.

Use a single `strictconcat` aggregate to combine tokens in order of location,
instead of computing a `rank` followed by a `concat`.

Strictness introduces a slight change of behaviour because missing tokens will now result
in no results from the predicate rather than an empty feature string.

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

@@ -127,23 +127,20 @@ module FunctionBodies {
     // If a function has more than 256 body subtokens, then featurize it as absent. This
     // approximates the behavior of the classifer on non-generic body features where large body
     // features are replaced by the absent token.
-    if count(DatabaseFeatures::AstNode node, string token | bodyTokens(entity, node, token)) > 256
+    if
+      strictcount(DatabaseFeatures::AstNode node, string token | bodyTokens(entity, node, token)) >
+        256
     then result = ""
     else
       result =
-        concat(int i, string rankedToken |
-          rankedToken =
-            rank[i](DatabaseFeatures::AstNode node, string token, Location l |
+        strictconcat(DatabaseFeatures::AstNode node, string token, Location l |
           bodyTokens(entity, node, token) and l = node.getLocation()
         |
-              token
+          token, " "
           order by
             l.getFile().getAbsolutePath(), l.getStartLine(), l.getStartColumn(), l.getEndLine(),
             l.getEndColumn(), token
         )
-        |
-          rankedToken, " " order by i
-        )
   }
 }