Update to protolude 0.3.0

The good part is that protolude 0.3.0 builds with GHC 8.10.

The bad part is that this change is a bit painful:
- the default `toS` has changed to no longer convert to and from ByteString
- similarly, `show` no longer outputs ByteString

The changes here are pretty much minimal to keep things compiling; I didn't
see a nice way to work with the new ConvertText class, even though `toUtf8`
seems like it might help if used besides `toS` at just the right spots.

test/QueryCost.hs

@@ -10,7 +10,8 @@ import qualified Hasql.Transaction          as HT
 import qualified Hasql.Transaction.Sessions as HT
 import           Text.Heredoc
 
-import Protolude hiding (get)
+import Protolude      hiding (get, toS)
+import Protolude.Conv (toS)
 
 import PostgREST.QueryBuilder (requestToCallProcQuery)
 import PostgREST.Types