Add ktn_code:map/2

[elbrujohalcon]

Is your feature request related to a problem? Please describe

https://github.com/inaka/elvis_core/pull/395#issuecomment-2810045798

Describe the solution you'd like

I would like to have a function that will traverse the entire hierarchy of a node and its sub-nodes and will apply the same function to all of them.

Describe alternatives you've considered

https://github.com/inaka/elvis_core/pull/395/files#diff-09f8fecea082afba9afc4b986b837fb10f24a9e85d7e90fe1c5b5868f99638f7R1717-R1738

Additional Context

The original idea for the implementation of the PR linked above with this new function would've included ktn_code:map(fun remove_location/1, Nodes).