[applet] Improve presentation and tooltips for toolbar toggles

1. Increased the spacing between them so they don't blend into one
   another so much
2. Made the terminolgy in the Wi-Fi tooltip match how it's phrased
   elsewhere
3. Added some explanatory text for the airplane tooltip so it's more
   obvious what it does

BUG: 421371
FIXED-In: 5.20