These functions now accept both an ID and data_source parameter,
enabling plugins like mbsync and missing to retrieve metadata from the
correct source.
Update mbsync and missing plugins to use the restored functions with
explicit data_source parameters. Add data_source validation to prevent
lookups when the source is not specified.
Add get_metadata_source helper function to retrieve plugins by their
data_source name, cached for performance.
Add a configuration section that lists all options for each plugin.
List options in alphabetic order.
Mention the default value for each option.
Use same sentences to describe concepts common to different plugins eg 'auto
option, install description
