Revise 'Add trackers' dialog

* Now it allow user to add tracker to different tier.
* The downloaded trackers are now displayed as is (without modifying).
* Now the dialog remember dialog size and last used URL.

Closes #17692.

src/base/bittorrent/trackerentry.cpp

@@ -28,6 +28,34 @@
 
 #include "trackerentry.h"
 
+#include <QList>
+#include <QVector>
+
+QVector<BitTorrent::TrackerEntry> BitTorrent::parseTrackerEntries(const QStringView str)
+{
+    const QList<QStringView> trackers = str.split(u'\n');  // keep the empty parts to track tracker tier
+
+    QVector<BitTorrent::TrackerEntry> entries;
+    entries.reserve(trackers.size());
+
+    int trackerTier = 0;
+    for (QStringView tracker : trackers)
+    {
+        tracker = tracker.trimmed();
+
+        if (tracker.isEmpty())
+        {
+            if (trackerTier < std::numeric_limits<decltype(trackerTier)>::max())  // prevent overflow
+                ++trackerTier;
+            continue;
+        }
+
+        entries.append({tracker.toString(), trackerTier});
+    }
+
+    return entries;
+}
+
 bool BitTorrent::operator==(const TrackerEntry &left, const TrackerEntry &right)
 {
     return (left.url == right.url);