I am glad to report that the variable unshadowing effort is finally complete.
The patches are posted and ready for review at GitLab merge request 3410. This merge request contains 59 commits, including the one enabling the warning in CMake configuration from Paul Bauer. If necessary, I can make the set of patches more granular e.g. by splitting local variable renames or less granular e.g. by joining class/struct member renames by module.
I would also like to update the Developer guide, however briefly. Perhaps Style guidelines would be a good place to add the details about avoiding variable shadowing in the future. I am open to suggestions/ideas how to document this.