HUD consumes 100% CPU

#### Issue details
When MP starts by default and with the HUD visible, after connecting to a vehicle the Windows Task Manager is telling me MP is consuming 100% CPU.

When I hide the HUD (double click on it and minimize), CPU immediately goes back down to near 0%.

When at 100%, the UI in MP feels slow and sluggish, buttons take time to click, it lags to go from one tab to another, etc.

I took the habit of minimizing the HUD as soon as MP starts and only show it when I fly, but it would be great if the HUD wouldn't consume that much CPU.

#### Version
All versions, the one I'm using now is 1.3.70 build 1.3.7277.34800

#### Platform
[X] All
[ ] AntennaTracker
[ ] Copter
[ ] Plane
[ ] Rover
[ ] Sub

Reproduce the issue by starting Mission Planner with the HUD visible, connecting to a vehicle, and comparing CPU use with the HUD minimized. Profile the HUD-related rendering or update path and verify that CPU usage drops substantially while the HUD remains visible and the interface stays responsive.

Written by the indexing model from the issue text.