Removing old references to populate_repo_browser

Removed references to populate_repo_browser in controller, tests and routes config; copied submissions_controller.rb to lib/benchmarking/submission_files/ to update it.
Unused block argument - `key`. If it's necessary, use `_` or `_key` as an argument name to indicate that it won't be used.<br>Unused block argument - `v2`. If it's necessary, use `_` or `_v2` as an argument name to indicate that it won't be used.<br>Avoid using `rescue` in its modifier form.