fix(S3 View): Display bucket contents with specific IAM role policies aws#4644

## Problem: 
S3 tree view doesn't show contents with specific IAM role policies.
Prefix parameter was null.

## Solution: 
Set Prefix parameter to an empty string as default. Allows bucket
contents display if root prefix is allowed.

ref: aws#4643

Author: avsthiago

.changes/next-release/Bug Fix-77137e24-593d-4859-a15f-e029edf843a7.json

@@ -0,0 +1,4 @@
+{
+	"type": "Bug Fix",
+	"description": "Resource Explorer: S3 tree view now shows bucket contents correctly, even when restricted to root prefix."
+}

packages/core/src/shared/clients/s3Client.ts

@@ -19,6 +19,7 @@ import { toStream } from '../utilities/collectionUtils'
 
 export const DEFAULT_MAX_KEYS = 300 // eslint-disable-line @typescript-eslint/naming-convention
 export const DEFAULT_DELIMITER = '/' // eslint-disable-line @typescript-eslint/naming-convention
+export const defaultPrefix = ''
 
 export type Bucket = InterfaceNoSymbol<DefaultBucket>
 export type Folder = InterfaceNoSymbol<DefaultFolder>
@@ -460,7 +461,13 @@ export class DefaultS3Client {
                 Bucket: bucket.name,
                 Delimiter: DEFAULT_DELIMITER,
                 MaxKeys: request.maxResults ?? DEFAULT_MAX_KEYS,
-                Prefix: request.folderPath,
+                /**
+                 * Set '' as the default prefix to ensure that the bucket's content will be displayed
+                 * when the user has at least list access to the root of the bucket.
+                 * https://github.com/aws/aws-toolkit-vscode/issues/4643
+                 * @default '' 
+                 */
+                Prefix: request.folderPath ?? defaultPrefix,
                 ContinuationToken: request.continuationToken,
             })
             .promise()