Enhancement: Text warning improvments

#### Issue details
HUD Red Text warnings are displayed one at a time, which presents a problem when there are multiple errors and the operator cannot tell all the things that are popping a critical error.

Also, these errors pop up and persist for some time regardless of whether the issue has been resolved or not.

I suggest the warnings are displayed in a list (most recent on top), and that errors that are currently active are Red, but that they change to another color (orange?) when the condition resolves, before disappearing.

It happens every so often that I will briefly lose my RC receiver, and the guy on the ground station sees the error pop up, but cannot tell when/if it's been resolved. And during ground operations, it is, of course, common to have multiple warning conditions at the same time, particularly during start, and it would be nice to see all these at the same time and watch them fall off, and not have to wait for the AHRS to settle before finding out you have a bag logging message hiding behind it.

#### Version
MP 1.3.68.1

Start by reproducing the HUD red-warning behavior in Mission Planner with multiple simultaneous errors and a receiver connection that briefly drops. Trace how warnings are displayed, retained, and removed; done means active warnings can be seen together, resolved warnings change state before disappearing, and the behavior is verified for the described ground-operation scenarios.

Written by the indexing model from the issue text.