Add multi-code-unit characters to length validation tests

Server implementations that naively use code units instead of code points to
evaluate length constraints will give incorrect results. This adds parameters
to the existing string length tests that use multi-code-unit characters to
generate strings that will meet the constraints if code units are counted,
but properly fail the constraints if code points are counted.

Fixes #1090

Author: adamthom-amzn

smithy-aws-protocol-tests/model/restJson1/validation/malformed-length.smithy

@@ -92,8 +92,8 @@ apply MalformedLength @httpMalformedRequestTests([
             }
         },
         testParameters: {
-            value: ["a", "abcdefghijklmnopqrstuvwxyz"],
-            inputLength: ["1", "26"]
+            value: ["a", "abcdefghijklmnopqrstuvwxyz", "👍"],
+            inputLength: ["1", "26", "1"]
         }
     },
     {
@@ -409,8 +409,8 @@ apply MalformedLengthOverride @httpMalformedRequestTests([
             }
         },
         testParameters: {
-            value: ["abc", "abcdefg"],
-            inputLength: ["3", "7"]
+            value: ["abc", "abcdefg", "👍👍👍"],
+            inputLength: ["3", "7", "3"]
         }
     },
     {