CustomScrollbar: migrated styles from sass to emotion (#30506)

* CustomScrollbar: migrated styles from sass to emotion

* fixes frontend test

* updated changes

* fixed page props and applied changes to all occurences

* moved the getStyles function to the bottom of the file

* made some changes

* fixed snapshot test

* Revert "Merge branch 'refactor-customscrollbar-30354' of https://github.com/grafana/grafana into refactor-customscrollbar-30354"

This reverts commit c45ee30b6b297991a1628e9b21c4121dc78e376c, reversing
changes made to d2645534e3.

* improved props name

* made use of theme variables for style consistency

* fixed snapshot test and updated some theme changes

* removed hover effects from customScrollbar style

* made some changes

* updated some changes

* added label to class names

* changed to a functional component and improved styling

* fixes snapshot test

* fixes small nit

* minor tweaks

Co-authored-by: Torkel Ödegaard <torkel@grafana.com>

public/app/core/components/Page/Page.tsx

@@ -47,7 +47,7 @@ class Page extends Component<Props> {
     const { navModel, children, ...otherProps } = this.props;
     return (
       <div {...otherProps} className="page-scrollbar-wrapper">
-        <CustomScrollbar autoHeightMin={'100%'} className="custom-scrollbar--page">
+        <CustomScrollbar autoHeightMin={'100%'}>
           <div className="page-scrollbar-content">
             <PageHeader model={navModel} />
             {children}