feat(storage): add samples and system tests for bucket encryption enforcement

[thiyaguk09]

Description

Adds comprehensive code samples and system tests to verify Google-managed,
Customer-managed, and Customer-supplied encryption enforcement logic.

• Add setBucketEncryptionEnforcementConfig.js sample
• Add getBucketEncryptionEnforcementConfig.js sample
• Add updateBucketEncryptionEnforcementConfig.js sample
• Add system tests to verify CLI output and backend metadata state
• Ensure server-side effectiveTime is correctly captured and displayed

Checklist

• I have followed guidelines from CONTRIBUTING.MD and Samples Style Guide
• Tests pass: npm test (see Testing)
• Lint pass: npm run lint (see Style)
• Required CI tests pass (see CI testing)
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• This pull request is from a branch created directly off of GoogleCloudPlatform/nodejs-docs-samples. Not a fork.
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new sample directory, and I created GitHub Actions workflow for this sample
• This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• Please merge this PR for me once it is approved

Note: Any check with (dev), (experimental), or (legacy) can be ignored and should not block your PR from merging (see CI testing).

[snippet-bot]

Here is the summary of changes.

You are about to add 3 region tags.

• storage/getBucketEncryptionEnforcementConfig.js:23, tag storage_get_encryption_enforcement_config
• storage/setBucketEncryptionEnforcementConfig.js:26, tag storage_set_encryption_enforcement_config
• storage/updateBucketEncryptionEnforcementConfig.js:23, tag storage_update_bucket_encryption_enforcement_config

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[gemini-code-assist]

Code Review

This pull request introduces three new code samples and corresponding system tests for managing bucket encryption enforcement configurations in Google Cloud Storage. The new samples demonstrate how to retrieve, set, and update or clear enforcement settings for Google-managed (GMEK), customer-managed (CMEK), and customer-supplied (CSEK) encryption. I have no feedback to provide as there are no review comments to evaluate.

[chandra-siri]

Approved by Jetski on behalf of chandrasiri