Drop support of Qt 5

Also remove usage of some deprecated stuff.

PR #19338.

src/base/path.cpp

@@ -377,11 +377,7 @@ QDataStream &operator>>(QDataStream &in, Path &path)
     return in;
 }
 
-#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
 std::size_t qHash(const Path &key, const std::size_t seed)
-#else
-uint qHash(const Path &key, const uint seed)
-#endif
 {
     return ::qHash(key.data(), seed);
 }