Fix update_lints
This fixes a bug in update_lints, where `internal` lints were not registered properly. This also cleans up some code. For example: The code generation functions no longer filter the lints the are given. This is now the task of the caller. This way, it is more obvious in the `replace_in_file` calls which lints will be included in which part of a file.
This also turns the lint modules private. There is no need for them to be public, since shared code should be in the utils module anyway.
And last but not least, this fixes the `register_lints` code generation, so also internal lints get registered.
changelog: none
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