Add support for encoding parameters in `wrap_in_private_key_info` and
`wrap_in_subject_public_key_info` as well as turn `Span<int>` into
`Span<int const>`.
Each of these strings would previously rely on StringView's char const*
constructor overload, which would call __builtin_strlen on the string.
Since we now have operator ""sv, we can replace these with much simpler
versions. This opens the door to being able to remove
StringView(char const*).
No functional changes.
