While reviewing https://github.com/certbot/certbot/pull/8404, it occurred to me that we're keeping both the generated files and the script used to generate them in `git`. Keeping both around seems unnecessary and is almost asking for the files to get out of sync at some point in the future. I fixed that by removing the files, adding them to `.gitignore`, and updating `build_remote.py` to generate them as needed.
* Remove generated files.
* Add generated files to gitignore.
* Reuse generate_dnsplugins_all.sh in build_remote