Migrate away from deprecated Qt functions

`QString QDateTime::toString(Qt::DateFormat format = Qt::TextDate)` will
be removed in Qt6.

src/gui/addnewtorrentdialog.cpp

@@ -655,7 +655,7 @@ void AddNewTorrentDialog::setupTreeview()
 
         // Set torrent information
         m_ui->labelCommentData->setText(Utils::Misc::parseHtmlLinks(m_torrentInfo.comment().toHtmlEscaped()));
-        m_ui->labelDateData->setText(!m_torrentInfo.creationDate().isNull() ? m_torrentInfo.creationDate().toString(Qt::DefaultLocaleShortDate) : tr("Not available"));
+        m_ui->labelDateData->setText(!m_torrentInfo.creationDate().isNull() ? QLocale().toString(m_torrentInfo.creationDate(), QLocale::ShortFormat) : tr("Not available"));
 
         // Prepare content tree
         m_contentModel = new TorrentContentFilterModel(this);

src/gui/log/logmodel.cpp

@@ -155,7 +155,7 @@ LogMessageModel::LogMessageModel(QObject *parent)
 
 void LogMessageModel::handleNewMessage(const Log::Msg &message)
 {
-    const QString time = QDateTime::fromMSecsSinceEpoch(message.timestamp).toString(Qt::SystemLocaleShortDate);
+    const QString time = QLocale::system().toString(QDateTime::fromMSecsSinceEpoch(message.timestamp), QLocale::ShortFormat);
     const QString messageText = message.message;
     const QColor foreground = m_foregroundForMessageTypes[message.type];
 
@@ -173,7 +173,7 @@ LogPeerModel::LogPeerModel(QObject *parent)
 
 void LogPeerModel::handleNewMessage(const Log::Peer &peer)
 {
-    const QString time = QDateTime::fromMSecsSinceEpoch(peer.timestamp).toString(Qt::SystemLocaleShortDate);
+    const QString time = QLocale::system().toString(QDateTime::fromMSecsSinceEpoch(peer.timestamp), QLocale::ShortFormat);
     const QString message = peer.blocked
             ? tr("%1 was blocked. Reason: %2.", "0.0.0.0 was blocked. Reason: reason for blocking.").arg(peer.ip, peer.reason)
             : tr("%1 was banned", "0.0.0.0 was banned").arg(peer.ip);

src/gui/properties/propertieswidget.cpp

@@ -319,7 +319,7 @@ void PropertiesWidget::loadTorrentInfos(BitTorrent::TorrentHandle *const torrent
     if (m_torrent->hasMetadata())
     {
         // Creation date
-        m_ui->labelCreatedOnVal->setText(m_torrent->creationDate().toString(Qt::DefaultLocaleShortDate));
+        m_ui->labelCreatedOnVal->setText(QLocale().toString(m_torrent->creationDate(), QLocale::ShortFormat));
 
         m_ui->labelTotalSizeVal->setText(Utils::Misc::friendlyUnit(m_torrent->totalSize()));
 
@@ -457,11 +457,11 @@ void PropertiesWidget::loadDynamicData()
             m_ui->labelUpSpeedVal->setText(tr("%1 (%2 avg.)", "%1 and %2 are speed rates, e.g. 200KiB/s (100KiB/s avg.)")
                 .arg(Utils::Misc::friendlyUnit(m_torrent->uploadPayloadRate(), true), ulAvg));
 
-            m_ui->labelLastSeenCompleteVal->setText(m_torrent->lastSeenComplete().isValid() ? m_torrent->lastSeenComplete().toString(Qt::DefaultLocaleShortDate) : tr("Never"));
+            m_ui->labelLastSeenCompleteVal->setText(m_torrent->lastSeenComplete().isValid() ? QLocale().toString(m_torrent->lastSeenComplete(), QLocale::ShortFormat) : tr("Never"));
 
-            m_ui->labelCompletedOnVal->setText(m_torrent->completedTime().isValid() ? m_torrent->completedTime().toString(Qt::DefaultLocaleShortDate) : "");
+            m_ui->labelCompletedOnVal->setText(m_torrent->completedTime().isValid() ? QLocale().toString(m_torrent->completedTime(), QLocale::ShortFormat) : QString {});
 
-            m_ui->labelAddedOnVal->setText(m_torrent->addedTime().toString(Qt::DefaultLocaleShortDate));
+            m_ui->labelAddedOnVal->setText(QLocale().toString(m_torrent->addedTime(), QLocale::ShortFormat));
 
             if (m_torrent->hasMetadata())
             {

src/gui/rss/rsswidget.cpp

@@ -486,7 +486,7 @@ void RSSWidget::handleCurrentArticleItemChanged(QListWidgetItem *currentItem, QL
         QString::fromLatin1("<div style='border: 2px solid red; margin-left: 5px; margin-right: 5px; margin-bottom: 5px;'>") +
         QString::fromLatin1("<div style='background-color: \"%1\"; font-weight: bold; color: \"%2\";'>%3</div>").arg(highlightedBaseColor, highlightedBaseTextColor, article->title());
     if (article->date().isValid())
-        html += QString::fromLatin1("<div style='background-color: \"%1\";'><b>%2</b>%3</div>").arg(alternateBaseColor, tr("Date: "), article->date().toLocalTime().toString(Qt::SystemLocaleLongDate));
+        html += QString::fromLatin1("<div style='background-color: \"%1\";'><b>%2</b>%3</div>").arg(alternateBaseColor, tr("Date: "), QLocale::system().toString(article->date().toLocalTime()));
     if (!article->author().isEmpty())
         html += QString::fromLatin1("<div style='background-color: \"%1\";'><b>%2</b>%3</div>").arg(alternateBaseColor, tr("Author: "), article->author());
     html += "</div>"

src/gui/transferlistmodel.cpp

@@ -361,9 +361,9 @@ QString TransferListModel::displayValue(const BitTorrent::TorrentHandle *torrent
     case TR_TAGS:
         return tagsString(torrent->tags());
     case TR_ADD_DATE:
-        return torrent->addedTime().toLocalTime().toString(Qt::DefaultLocaleShortDate);
+        return QLocale().toString(torrent->addedTime().toLocalTime(), QLocale::ShortFormat);
     case TR_SEED_DATE:
-        return torrent->completedTime().toLocalTime().toString(Qt::DefaultLocaleShortDate);
+        return QLocale().toString(torrent->completedTime().toLocalTime(), QLocale::ShortFormat);
     case TR_TRACKER:
         return torrent->currentTracker();
     case TR_DLLIMIT:
@@ -387,7 +387,7 @@ QString TransferListModel::displayValue(const BitTorrent::TorrentHandle *torrent
     case TR_COMPLETED:
         return unitString(torrent->completedSize());
     case TR_SEEN_COMPLETE_DATE:
-        return torrent->lastSeenComplete().toLocalTime().toString(Qt::DefaultLocaleShortDate);
+        return QLocale().toString(torrent->lastSeenComplete().toLocalTime(), QLocale::ShortFormat);
     case TR_LAST_ACTIVITY:
         return lastActivityString((torrent->isPaused() || torrent->isChecking()) ? -1 : torrent->timeSinceActivity());
     case TR_AVAILABILITY: