It may be handy to have some sort of storage inspector at some point but
for now, it doesn't make sense to open a database file. So only allow
opening script files, and don't make assumptions on their extension.
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.