console.lua: say focused instead of selected

The selected term was causing confusion e.g. in
https://github.com/mpv-player/mpv/pull/15711#issuecomment-2676060139.
Saying either focused or current makes more sense since the item is not
actually selected until you click or press Enter.

DOCS/interface-changes/console-focused-color.txt

@@ -0,0 +1,2 @@
+rename `console-selected_color` script-opt to `console-focused_color`
+rename `console-selected_back_color` script-opt to `console-focused_back_color`