Refactor CSS Handling to Use Drupal's Asset Library System

Problem/Motivation

We can refactor the handling of CSS in acquia_optimize.module file at https://git.drupalcode.org/project/acquia_optimize/-/blob/1.x/acquia_opt...

Proposed resolution

1. Create library definition
2. Create CSS file
3. Update AJAX command at https://git.drupalcode.org/project/acquia_optimize/-/blob/1.x/acquia_opt...