Don't read unlimited data from files

It now guards against reading infinite files such as `/dev/zero`.
And most readings are bound with a (lax) limit.
As a side effect, more checking are done when reading a file and
overall the reading procedure is more robust.

PR #19095.

src/base/bittorrent/dbresumedatastorage.cpp

@@ -41,7 +41,6 @@
 
 #include <QByteArray>
 #include <QDebug>
-#include <QFile>
 #include <QMutex>
 #include <QSet>
 #include <QSqlDatabase>