[AXON-1599]: User message background color

[jwang19-atlassian]

What Is This Change?

1. User message in BBY and IDE will change to ADS color/background/accent/blue/bolder/default in this PR.
2. Fix dark theme detection

Before

After

BBY

IDE
Light Theme

Dark Theme

Light High Contrast Theme

Dark High Contrast Theme

How Has This Been Tested?

Basic checks:

• npm run lint
• npm run test

[atlassian]

The issue is ready for review, and the acceptance criteria have been met:

• ✅ Update the 'user message' bubble colour to match the Rovo 'user message' colour.
• ✅ Use the design token 'color/background/accent/blue/bolder/default' if applicable.

Check Jira issue

[atlassian]

The issue is ready for review, and the acceptance criteria have been met:

• ✅ Update the 'user message' bubble colour to match the Rovo 'user message' colour.
• ✅ Use the design token 'color/background/accent/blue/bolder/default' if applicable.

Check Jira issue