Custom objective names for a given set of goals

Sets of goals (i.e. overall objectives) should be added into the script as curated objectives, sort of like presets or built-in challenges. Only the names has to be added for this feature, but ideally the player should be able to selected a curated objective or select "custom" and create their own as they do now.

The hard part would probably be figuring out how to integrate it into OpenTTD's config window, as GSInfo (in the GS API) is basically all that is available for this.

Start by reviewing the OpenTTD config window integration and the script's use of GSInfo, which the issue identifies as the available GS API. Define how curated objective names, curated selection, and the existing custom-objective flow should fit together; done means players can choose a curated objective or select custom and create objectives as before.

Written by the indexing model from the issue text.