[bash] Fix CTRL-R to preserve the latest yank

Close #1216

1. Append a single space so that step 3 won't fail
2. CTRL-E to move to the end of the line
3. CTRL-U to delete the whole line before the cursor
4. CTRL-Y to paste the deleted line
5. ESC+Y to rotate the kill ring and bring back the previous yank before step 3
6. CTRL-U to delete the whole line again
7. Paste `__fzf_history__`
8. ESC+CTRL-E to expand the command substitution
9. ESC+R to redraw the line
10. ESC+^ to expand the history entry (!NUMBER)