This adds a further simplification in packaging of section and config data for a config-sync request, motivated (and made possible) by the extensions in T6121. In order to invoke priority ordering on the target host, these commands were batched in a single request in a subsequent task. However, continuing the extensions of T6121, it is inconvenient to use the method get_config_dict for individual section bodies when the section indicates a leaf node, suggesting the idea of packaging all section paths, respectively, section bodies as (config)tree structures represented as dicts: consider the section paths as a mask, and the section bodies as the config subtree under the mask; a simple configtree function mask_inclusive supports the needed marshalling. This allows a single command that avoids get_config_dict and the need for batching. As a test case, the section ['system', 'timezone'] is added.