Python: Copy board iterables to prevent segfaults

Python code like:
for track in board.GetTracks():
  board.Remove(track)

Would delete tracks in the the underlying m_tracks while iterating over
it.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/5192

pcbnew/python/swig/board.i

@@ -133,9 +133,11 @@ HANDLE_EXCEPTIONS(BOARD::TracksInNetBetweenPoints)
         except:
             self.this = this
 
-    def GetFootprints(self):          return self.Footprints()
-    def GetDrawings(self):            return self.Drawings()
-    def GetTracks(self):              return self.Tracks()
+    # Convert these to lists to keep users from using them to delete
+    # items in the iterable while looping over it
+    def GetFootprints(self):          return list(self.Footprints())
+    def GetDrawings(self):            return list(self.Drawings())
+    def GetTracks(self):              return list(self.Tracks())
 
     def Save(self,filename):
         return SaveBoard(filename,self)