generate util functions to consume response stream

[AllanZhengYP]

Issue #, if available:
Generated change PR: aws/aws-sdk-js-v3#3795

Description of changes:
Now if the deserialized object has streaming blob member(SSDK's input or SDK's output), customers can tranform the stream into string by

const body = response.Body;
const str = await body.transformToString("utf-8");

Or get the binary data by:

const binaryData: Uint8Array = await resp.Body.transformToByteArray();
// using buffer
const buf: Buffer = Buffer.from(await resp.Body.transformToByteArray());

Or transform to runtime-agnostic WebStream by:

// browsers and Node.js 16.5+
const webstream: ReadableStream = resp.Body.transformToWebStream();
const data = await webstream.json();
const buf = await webstream.arrayBuffer();

The output stream payload's interface is still assignable to the stream payload shape in the input, so this will work:

  new PutObjectCommand({ Body: bucket1Response.Body, Bucket: "Bucket2" });

At the same time, the payload stream is still an instance of the runtime-specific stream implementation, i.e. Stream.Readable in Node.js, ReadableStream in browsers and Blob in React Native. So the code like below will still work:

if (resp.Body instance of ReadableStream) {
  // Handle web stream
}

For SSDK, nothing changed other than operation input shape containing streaming blob member will more strict, for example:

diff --git a/private/aws-restjson-server/src/server/operations/StreamingTraits.ts b/private/aws-restjson-server/src/server/operations/StreamingTraits.ts
index a38915aeae..8a114617c4 100644
--- a/private/aws-restjson-server/src/server/operations/StreamingTraits.ts
+++ b/private/aws-restjson-server/src/server/operations/StreamingTraits.ts
@@ -137,16 +137,7 @@ export class StreamingTraitsHandler<Context> implements __ServiceHandler<Context
 
 export type StreamingTraits<Context> = __Operation<StreamingTraitsServerInput, StreamingTraitsServerOutput, Context>;
 
-type StreamingTraitsServerInputType = Omit<StreamingTraitsInputOutput, "blob"> & {
-  /**
-   * For *`StreamingTraitsInputOutput["blob"]`*, see {@link StreamingTraitsInputOutput.blob}.
-   */
-  blob?: StreamingTraitsInputOutput["blob"] | string | Uint8Array | Buffer;
-};
-/**
- * This interface extends from `StreamingTraitsInputOutput` interface. There are more parameters than `blob` defined in {@link StreamingTraitsInputOutput}
- */
-export interface StreamingTraitsServerInput extends StreamingTraitsServerInputType {}
+export interface StreamingTraitsServerInput extends StreamingTraitsInputOutput {}
 export namespace StreamingTraitsServerInput {
   /**
    * @internal

It should be OK as the type exposed to SSDK customers are more strict.

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[kuhe]

continued in #593