Remove, use, or require empty dots in `new_epi_df`

[brookslogan]

The dots (...) in new_epi_df are unused. Misspelling argument names or forgetting the interface can result in swapping in defaults rather than raising an error. (E.g., new_epi_df(....., other_keys = "age_group") --- this is not the current way to set other_keys metadata, but will not raise an error, instead continuing on without setting this metadata.)

We should either remove the dots arg altogether, use it in some way, or check that it is empty. Last part could use ellipsis::check_dots_empty() if its messages are all right or rlang::dots_n(...) with custom messaging.