fix(column)!: ensure 'statuscolumn' works with virtual and wrapped lines

Problem:    The `'statuscolumn'` was not re-evaluated for wrapped lines,
            when preceded by virtual/filler lines. There was also no way
            to distinguish virtual and wrapped lines in the status column.
Solution:   Make sure to rebuild the statuscolumn, and replace variable
            `v:wrap` with `v:virtnum`. `v:virtnum` is negative when drawing
            virtual lines, zero when drawing the actual buffer line, and
            positive when drawing the wrapped part of a buffer line.

src/nvim/eval.h

@@ -166,7 +166,7 @@ typedef enum {
   VV__NULL_BLOB,  // Blob with NULL value. For test purposes only.
   VV_LUA,
   VV_RELNUM,
-  VV_WRAP,
+  VV_VIRTNUM,
 } VimVarIndex;
 
 /// All recognized msgpack types