Display battery usage on bluetooth radio screen

[gabek]

What changed?

This change adds the battery level to the bluetooth radio status screen. The discussion came up in #837. Closes #847

Why did it change?

I felt the battery status should be surfaced more conveniently, since it is a common value to be looking at.

Screenshots/Videos (when applicable)

Checklist

• [x] My code adheres to the project's coding and style guidelines.
• [x] I have conducted a self-review of my code.
• [ ] I have commented my code, particularly in complex areas.
• [ ] I have made corresponding changes to the documentation.
• [x] I have tested the change to ensure that it works as intended.