FlightPlanner: fix zero-alt warning for ArduPlane

[robertlong13]

Draft PR. I've run out of time today. I'll try to come back to this next week or Andras can maybe finish it; just want to get what I have out there.

So, on Copter, pretty much any nav command with 0 altitude means "keep current altitude". On Plane, this is only true for loiters (and only relative altitude). Waypoints in plane will happily use 0 as a true 0. I haven't tested across different releases yet.

I only just realized this today. The recent addition trying to inform users about the nuances of 0-alt commands (#3574) is actually dangerously wrong for plane users.

We probably need an emergency release after this.

TODO:

• The showagain form doesn't play nice with long messages. I need to try to fix that without changing the old warnings too much:

• I only partially applied the rename of the existing warning variable. The designer didn't apply the rename in the other languages.
• The new warning needs the german translation

[robertlong13]

I have overhauled MessageShowAgain to support longer messages:

and confirmed the old messages still look good

I also removed the blank placeholders in the languages that don't have a translation. Turns out that if you have a blank placeholder, then that's what gets printed. We don't want that. Leaving it out makes it fall back to the English translation.

TODO:

• Make sure my rework of MessageShowAgain isn't somehow going to piss off mono, MacOS, or Android. @meee1 are you able to test those? I can maybe try Android, but I remember it being a nightmare last time I tried.
• Check with Randy and Tridge to make sure they approve of the list of commands we warn about and the message that gets displayed.
• Andras to add a DE and UK translation of my new message

[robertlong13]

@meee1 the CI failure seems to be somehow unrelated to this PR (a recent change on the default runner maybe?). I just ran it on master on my fork and got the same error:

Xamarin.Android.Tooling.targets(100,5): error XA5207: Could not find android.jar for API level 33. This means the Android SDK platform for API level 33 is not installed. Either install it in the Android SDK Manager (Tools > Android > Android SDK Manager...), or change the Xamarin.Android project to target an API version that is installed. (C:\Program Files (x86)\Android\android-sdk\platforms\android-33\android.jar missing.) [D:\a\MissionPlanner\MissionPlanner\ExtLibs\Xamarin\GDAL\GDALMPAndroid.csproj]

Edit: got it to work by pinning the windows runner to Windows-2022 for the Android workflow

[robertlong13]

Discussed this on the dev call, and Tridge has signed off on the message and logic (for plane).

[meee1]

this is still in draft?

[robertlong13]

this is still in draft?

I was holding off to test the Android and mono builds just to be safe (been struggling to test it personally), and I wanted Andras to provide a translation for the new message, but I won't hold this up for it.

I'll just mark it ready.