Read only controls don't have a border, making their bounds hard
to see when not on the default surface color.

This change uses transparency to create subtle contrast against
any surface color.

- format category items nicer
- add functionality for active item

feat(GlDuoChat): improved styling for context menu category items

See merge request gitlab-org/gitlab-ui!4574



Merged-by: Savas Vedova <svedova@gitlab.com>
Approved-by: Savas Vedova <svedova@gitlab.com>
Reviewed-by: Elwyn Benson <ebenson@gitlab.com>
Co-authored-by: Elwyn Benson <ebenson@gitlab.com>

feat(DesignTokens): Update read-only control background color

See merge request gitlab-org/gitlab-ui!4561



Merged-by: Mark Florian <mflorian@gitlab.com>
Approved-by: Jeremy Elder <jelder@gitlab.com>
Approved-by: Mark Florian <mflorian@gitlab.com>
Co-authored-by: GitLab Bot <gitlab-bot@gitlab.com>
Co-authored-by: danmh <dmizzi-harris@gitlab.com>

# [91.7.0](gitlab-org/gitlab-ui@v91.6.0...v91.7.0) (2024-09-04)

### Features

* add improved duo chat context menu category items ([05bdfa06](gitlab-org/gitlab-ui@05bdfa06))
* **DesignTokens:** Update read-only control background color ([f6afc9a3](gitlab-org/gitlab-ui@f6afc9a3))