[SSDK] Fix validation generation and protocol tests

[adamthom-amzn]

Description of changes:
Streaming blob member inputs and design-time media types need special consideration during code generation, and the protocol tests were not accounting for the need for a validation customizer. Also, we weren't correctly generating validate for empty structures.

This does not impact SDK generation. Output of git status after yarn generate-clients:

On branch main
Your branch is ahead of 'origin/main' by 1 commit.
  (use "git push" to publish your local commits)

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
        modified:   protocol_tests/aws-query/tests/functional/awsquery.spec.ts

And that diff has the expected content

diff --git a/protocol_tests/aws-query/tests/functional/awsquery.spec.ts b/protocol_tests/aws-query/tests/functional/awsquery.spec.ts
index a26a08b573..01b6921209 100644
--- a/protocol_tests/aws-query/tests/functional/awsquery.spec.ts
+++ b/protocol_tests/aws-query/tests/functional/awsquery.spec.ts
@@ -548,9 +548,7 @@ it("QueryInvalidGreetingError:Error:GreetingWithErrors", async () => {
 /**
  * Parses customized XML errors
  */
-// Manually skipping to unblock smithy-1.8.x update.
-// TODO: Consume AWSQueryError trait as a follow-up.
-it.skip("QueryCustomizedError:Error:GreetingWithErrors", async () => {
+it("QueryCustomizedError:Error:GreetingWithErrors", async () => {
   const client = new QueryProtocolClient({
     ...clientParams,
     requestHandler: new ResponseDeserializationTestHandler(

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[JordonPhillips]

There is also a .isStringShape() method but eh

[JordonPhillips]

Also worth noting, for the JS team member that review this, that that diff shown should no longer happen as of aws/aws-sdk-js-v3#2506 as the skip will be generated.