Add SURFTRAK mode support for ArduSub

[ES-Alexander]

Fixes #786.

⚠️ UNTESTED - I just figured I'd get the code started, and hopefully someone can comment if there's something obvious I'm missing.

If possible it would be nice to have the mode and joystick button disabled for firmwares that don't support them (e.g. for non-ArduSub vehicles, and ArduSub <4.5), or at least provide an obvious warning when trying to switch to it (this may already happen if the vehicle rejects the mode change - not sure), but I'm not sure how to do either of those things.

@clydemcqueen may have some input as well.

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@rafaellehmkuhl as a small comment, it seems weird to me to have to put the same information in twice in the mavlink-manual-control.ts file - could the button function actions not be added dynamically using the MAVLinkButtonFunction enum?

[rafaellehmkuhl]

If possible it would be nice to have the mode and joystick button disabled for firmwares that don't support them (e.g. for non-ArduSub vehicles, and ArduSub <4.5), or at least provide an obvious warning when trying to switch to it (this may already happen if the vehicle rejects the mode change - not sure), but I'm not sure how to do either of those things.

We can add rules on Cockpit, although I think this should be on the vehicle side, otherwise we will have to keep track of every firmware change ever (e.g.: answering something like "Mode 13 does not exist in vehicle" would solve the problem). @Williangalvani what do you think?

@rafaellehmkuhl as a small comment, it seems weird to me to have to put the same information in twice in the mavlink-manual-control.ts file - could the button function actions not be added dynamically using the MAVLinkButtonFunction enum?

You can actually reuse the enum there on the end of line 239. I've tried different approachs and didn't like any and kept that in the end, but is open for improvement.