Add support for visual ranges ending with a newline

These primarily happen when first entering visual mode, but can also
be created with objects like `vi{`.

Along the way fix the way ranges like `vi{` are selected to be more
similar to nvim.

crates/vim/test_data/test_enter_visual_mode.json

@@ -10,3 +10,11 @@
 {"Key":"k"}
 {"Key":"b"}
 {"Get":{"state":"The «ˇquick brown\nfox jumps o»ver\nthe lazy dog","mode":{"Visual":{"line":false}}}}
+{"Put":{"state":"a\nˇ\nb\n"}}
+{"Key":"v"}
+{"Get":{"state":"a\n«\nˇ»b\n","mode":{"Visual":{"line":false}}}}
+{"Key":"v"}
+{"Get":{"state":"a\nˇ\nb\n","mode":"Normal"}}
+{"Put":{"state":"a\nb\nˇ"}}
+{"Key":"v"}
+{"Get":{"state":"a\nb\nˇ","mode":{"Visual":{"line":false}}}}