In addition, consistently speak of a 'selection prompt'.

The comment on max_length was simply outdated.

I'm not sure about the grammar or format of the comments, but open to changing it.

The comment of default() was misleading: if a default value is set,
the user can still change the selected answer. They merely have the
*additional* option of confirming the default choice.

Setting it to false doesn't make a difference in practice.

The distinction between self.height and self.prompt_height only matters
when calling TermThemeRenderer::clear_preserve_prompt(): that method preserves
prompts and only clears input below the most recent prompt.
However, the password prompt only calls TermThemeRenderer::clear(),
which treats height and prompt_height in the same way.

The function set_prompts_reset_height is now unused, hence is removed.