Fix the Bubbles game on TTY frames

Fix the Bubbles game on TTY frames

* lisp/play/bubbles.el (bubbles--col-offset)
(bubbles--row-offset): Doc fixes.
(bubbles--compute-offsets): Conflate the GUI and TTY code into
a single common version.  Set the offsets to simple numbers,
not to lists.
(bubbles--initialize, bubbles--show-scores): Wrap offset
values in a list, so that they are interpreted as pixel
values, not as units of character width.  This fixes the game
on TTY frames.  (Bug#32744)