* refactor: mark subclass' destructors as override.
* refactor: use QUrl to parse announce URL strings.
The prompt for this was to work around a clang-tidy issue where
"char* host = nullptr;" triggers a "don't use varargs" warning,
but on the other hand it's also terser / cleaner.
* refactor: make the TorrentDelegate brushes const.
* refactor: s/auto/auto const*/ where appropriate
* chore: add some nonconst global warning exemptions
* chore: turn off warnings in GTest
* refactor: just disable the clang-tidy warning.
Apparently a std::array<T>::iterator is a T* on clang, since clang-tidy's
readability warning says we should use 'auto*' instead of 'auto'. However
adding that annotation fails on MSVC, where the is apparently _not_ a raw
pointer.
Since there's not a way to satisfy both of them at the same time, disable
the warning.
