feat: Add filters to list flows

What does this merge request do and why?

This MR adds the ability to filter the list of flows returned by letting the client pass in filters for version, name and environment.

Related issue: #1530 (closed)

How to set up and validate locally

1. Run duo workflow service poetry run duo-workflow-service
2. Filter using grpc curl - grpcurl -plaintext -d '{"filters": {"environment": ["remote"]}}' localhost:50052 DuoWorkflow/ListFlows

Merge request checklist

• Tests added for new functionality. If not, please raise an issue to follow up.
• Documentation added/updated, if needed.
• If this change requires executor implementation: verified that issues/MRs exist for both Go executor and Node executor or confirmed that changes are backward-compatible and don't break existing executor functionality.