feat: Add storage type and Google Storage settings to worker

[KiyotakaMatsushita]

Description

This change adds support for using Google Cloud Storage as the storage backend for user files in Dify. It introduces two new environment variables for configuring Google Storage: GOOGLE_STORAGE_BUCKET_NAME and GOOGLE_STORAGE_SERVICE_ACCOUNT_JSON_BASE64. When STORAGE_TYPE is set to google-storage, these variables will be used to connect to and store files in a Google Storage bucket.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update, included: Dify Document
• Improvement, including but not limited to code refactoring, performance optimization, and UI/UX improvement
• Dependency upgrade

How Has This Been Tested?

• Tested setting STORAGE_TYPE=google-storage and providing valid values for GOOGLE_STORAGE_BUCKET_NAME and GOOGLE_STORAGE_SERVICE_ACCOUNT_JSON_BASE64
• Verified user files are successfully stored in and retrieved from the configured Google Storage bucket
• Ensured existing storage backends (local, S3, Azure Blob) continue to function as expected

Suggested Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes