update message bar to use semantic tokens

[rachethecreator]

Update to semantic tokens where applicable for react-message-bar Add fallback values to fluentOverrides

Gaps noted here

Kumo implementation here

Figma design here

Previous Behavior

Used fluentui/tokens

New Behavior

Used fluentui/semantic-tokens if a replacement exists

[github-actions[bot]]

Pull request demo site: URL

[Mitch-At-Work]

Looks good, just one small visual regression

Let's investigate why the button boldness is different between current prod and semantic styles:

[rachethecreator]

Looks good, just one small visual regression

Let's investigate why the button boldness is different between current prod and semantic styles:

Looks like it's directly due to the Button component. The small size should have regular font weight, but is mapped to have semibold, like the medium and large sizes. Fixed this in the following commit in Button.