positional indicators for filter, choose, and others, like we did on tables

[caarlos0]

see #839

[FilipeBento]

My only advice would be to consider that gum filter might want a slightly different behavior than the one implemented on #839.

You might want [line_pos]/[number_of_filtered_lines]/[total_lines] instead of just [line_pos]/[total_lines].
I believe it is more useful this way. This is the behavior implemented in fzf. The indicators update with the filtering query.
In the end it is up to the amazing devs to decide :)

(screenshot to help clarify)