Epic: Accessible chart themes in Grafana

### Summary We are planning to introduce new color themes for use on Grafana dashboards. These themes will not only add visual variety to the platform, but will also address accessibility concerns. These will cater to the visual needs of users with various conditions, such as color vision deficiency, low visual acuity, and contrast sensitivity. These improvements will help to ensure that Grafana is accessible and usable for all users, regardless of their visual abilities.