Rename variable $input-border-focus to $input-border-color-focus (#22413)

Rename variable $input-border-focus to $input-border-color-focus (#22413)

* Rename variable $input-border-focus to $input-border-color-focus
* Rename variables $pagination-hover-border, $pagination-active-border, $pagination-disabled-border to $pagination-hover-border-color, $pagination-active-border-color, $pagination-disabled-border-color, respectively
* Rename variables $state-*-border to $state-*-border-color, respectively
* Rename variables $alert-*-border to $alert-*-border-color
* Rename $list-group-active-border to $list-group-active-border-color
* Rename $table-inverse-border to $table-inverse-border-color
* Rename $btn-*-border to $btn-*-border-color
* Rename $navbar-*-toggler-border to $navbar-*-toggler-border-color