Allow matcher custom failure messages to be a function

By deferring the evaluation of these messages, we can avoid the
expensive creation of them when in the majority use case (tests are
    passing) they are not needed.

These failure messages were causing performance problems with larger
objects needed to be pretty printed as discussed in #520 and brought up
by @rdy.

[fixes #65925900][fixes #520]

src/core/Expectation.js

@@ -43,7 +43,11 @@ getJasmineRequireObj().Expectation = function() {
           args.unshift(name);
           message = this.util.buildFailureMessage.apply(null, args);
         } else {
-          message = result.message;
+          if (Object.prototype.toString.apply(result.message) === "[object Function]") {
+            message = result.message();
+          } else {
+            message = result.message;
+          }
         }
       }