Enable -Werror=missing-methods and -Werror=missing-fields in Stackage builds

See https://github.com/ghc-proposals/ghc-proposals/issues/544

There are a handful of packages for which the fix will probably not happen timely (e.g. `network-info` issue https://github.com/jacobstanley/network-info/issues/20 is quite old)

But for many packages, e.g. `monad-logger` the omission of method definition is probably just because no CI have yelled at the author. Warnings are very easy to ignore, but IMHO these two warnings are *rarely* ever a false positives. (And my experiment in https://github.com/ghc-proposals/ghc-proposals/issues/544 shows that there are practically none).