Add End-to-End integration test pipeline for all databases with backup and restore validation

Description:

We should write a manual pipeline to fully test features across all supported databases to ensure reliability in production environments.

Proposed Workflow:

For each database supported by the operator, the pipeline should perform the following actions locally:

Create Local Database Instance: Spin up a local instance of the database.

Apply Manifests: Generate and apply the operator manifests (e.g., Database CRD, Storage CRD, and Backup CRD).

Trigger & Verify Backup: Execute the backup process and push the exported files into a target storage backend like a local MinIO instance or an S3 bucket.

Perform Restore Validation: Download the backup artifact and execute a full restore, confirming that data integrity remains intact.

This automated testing flow will serve as our primary validation mechanism to guarantee all features work seamlessly prior to production deployment.

Further questions:

• Should it be a script and run manually or put it in CI/CD?
• Can we run e2e test parallel since there are so many databases?

No files, tests, or entry points are named. Start by inventorying the operator's supported databases and its manifest, backup, and restore workflows; resolve whether the pipeline is manual or CI/CD and whether runs should be parallel before defining completion as successful backup, restore, and data-integrity validation.