Add hack to fix off-by-one error in Vi-mode cancel-commandline

The new cursor-end-mode "inclusive" (which is active in Vi mode) is causing
many issues.

One of them is because cancel-commandline wants to move to the end of the
command line before printing "^C".  Since "inclusive" cursor mode prevents
the cursor from moving past the last character, that one will be overwritten
with a "^".  Hack around this.

Closes #11261

(cherry picked from commit b08ff33291)

src/reader.rs

@@ -2347,7 +2347,12 @@ fn handle_readline_command(&mut self, c: ReadlineCmd) {
                 if c == rl::CancelCommandline {
                     // Move cursor to the end of the line.
                     let end = self.command_line.len();
-                    self.update_buff_pos(EditableLineTag::Commandline, Some(end));
+                    {
+                        let tmp =
+                            std::mem::replace(&mut self.cursor_end_mode, CursorEndMode::Exclusive);
+                        self.update_buff_pos(EditableLineTag::Commandline, Some(end));
+                        self.cursor_end_mode = tmp;
+                    }
 
                     self.autosuggestion.clear();
                     // Repaint also changes the actual cursor position