feat(java): add deleteFolderRecursive sample

[nidhiii-27]

This adds a sample demonstrating how to recursively delete a folder in a hierarchical namespace bucket.

Fixes: b/521168740

[snippet-bot]

Here is the summary of changes.

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• java-storage/samples/snippets/src/main/java/com/example/storage/control/v2/DeleteFolderRecursive.java:19, tag storage_control_delete_folder_recursive

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[gemini-code-assist]

Code Review

This pull request introduces a new code snippet DeleteFolderRecursive.java to demonstrate recursive folder deletion using StorageControlClient, along with a corresponding integration test in FoldersTest.java. The feedback highlights two main improvements: simplifying the redundant throws clause in the deleteFolderRecursive method signature, and removing the unused gen1 variable assignment in the test method.

[gemini-code-assist]

The throws clause is redundant because Exception is a superclass of ExecutionException and InterruptedException. Declaring them together is unnecessary. We can simplify this by throwing only Exception.

Suggested change

	public static void deleteFolderRecursive(String bucketName, String folderName)
	throws ExecutionException, InterruptedException, Exception {
	public static void deleteFolderRecursive(String bucketName, String folderName)
	throws Exception {

[nidhiii-27]

Done

[gemini-code-assist]

The variable gen1 is declared but never used. You can invoke createFolder directly without assigning its return value to an unused variable.

    storageControl.createFolder(
        BucketName.of("_", bucket.getName()),
        Folder.getDefaultInstance(),
        folderName.getFolder());

[nidhiii-27]

Done