fix(ui2): fix ruler on repeated messages

Problem: a long message is cropped to keep the ruler visible. But when
the message is repeated, it can be written over the ruler, while the
repetition indicator "(1)" is still placed just before the ruler, which
ends up somewhere inside the message.

Solution: currently, long messages are only cropped when setting the
'last' virttext. Make sure this happens after a repeated long message.

test/functional/ui/messages2_spec.lua

@@ -1200,6 +1200,15 @@ describe('messages2', function()
       -----------------------------------0,0-1          All|
     ]])
     feed('<C-L>')
+    -- message with repetition indicator keeps ruler intact
+    command('echo "-"->repeat(&columns)')
+    command('echo "-"->repeat(&columns)')
+    screen:expect([[
+      ^                                                     |
+      {1:~                                                    }|*12
+      --------------------------------(1)0,0-1          All|
+    ]])
+    feed('<C-L>')
     -- when the ruler is configured smaller, there is more space for messages
     command('set rulerformat=%l | redraw | echo "-"->repeat(&columns)')
     screen:expect([[