* Remove `--bs-border-opacity: 1` from `.border-*` utilities
We set `--bs-border-opacity: 1` globally at the `:root` level, so redeclaring it on every `.border-*` utility doesn't make much sense. I think we can drop this.
* Remove global border-opacity var, restore on .border-color classes, move .border-color utils down the list to fix some specificity issues
* Add some demos of border utils to the docs
* Revert `border-color` change
* Add new border-color-translucent for when we want optional alpha-transparency in our border-color
Apply to drodpowns, modals, offcanvas, popovers, and toasts
* bundlewatch
- Updates the utilities mixin to check for specific CSS variable names via `css-variable`
- Bonus fix: we now prevent local variables for `0` value utilities (e.g., `.border-top-0` no longer sets `--bs-border-opacity: 1`
- Adds new `.border-opacity-*` classes
- Adds new root variables: `--bs-border-color`, `--bs-border-style`, `--bs-border-width`
- Documents the new variable changes
