Toolbar: add CSS from admin color scheme on front-end.

This changeset introduces the `wp_admin_bar_add_color_scheme_to_front_end()` which is hooked on `admin_bar_init` in order to use the CSS from admin color schemes on the admin bar on front-end, as inline styles.

Props sabernhardt, huzaifaalmesbah, audrasjb, johnbillion, noruzzaman, JeffPaul, joedolson, huzaifaalmesbah, amesplant, r1k0, shailu25.
Fixes #64762.



git-svn-id: https://develop.svn.wordpress.org/trunk@62025 602fd350-edb4-49c9-b593-d223f7449a82