Add functionality to allow tools.costs to use older version(s) of WEO data

[measrainsey]

While updating tools.costs to use the 2023 WEO data (instead of 2022 WEO data) in #187, @khaeru brought up the following point in his comment: should the tools.costs continue to update to use the latest WEO data releases in the future, how do we want to handle cases where users want to revert back to older versions of the WEO data (for checking, reproducibility, etc)?

The following suggestion from @khaeru would probably be the best long-term solution:

Provide a parameter or option (see for instance .tools.iea.web, or .model.snapshot) that allows the user to select the edition/version of input data used, and adjusts any other parameters to suit.

I'm creating this issue to document that the aforementioned functionablity would be good to have, so this is something I can work towards adding in the future (most likely with the help of @glatterf42 and/or @khaeru).