FalkorDB: add missing operations

[davidsbatista]

The DocumentStore is missing some DocumentStore methods, namely:

• delete_all_documents()
• delete_by_filter(filters)
• update_by_filter(filters, meta)
• count_documents_by_filter(filters)
• count_unique_metadata_by_filter(filters, metadata_fields)
• get_metadata_fields_info()
• get_metadata_field_min_max(metadata_field)
• get_metadata_field_unique_values(...)