AP_Scripting: add Lua bindings to check VTOL approach and land phases

[CallanDaniel]

This PR adds Lua bindings for the follwing functions from quadplane.h :

• in_vtol_land_approach()
• in_vtol_land_final()
• in_vtol_land_sequence()
• in_vtol_land_poscontrol()
• in_vtol_airbrake()

It also makes the functions public in order to expose them to Lua scritping.

Tested in SITL with the example script running:

[CallanDaniel]

@Hwurzburg @IamPete1 I added the empty line, but it seems to dissapear when I commit. Appologies for the confusion, still learning.

[IamPete1]

@Hwurzburg @IamPete1 I added the empty line, but it seems to dissapear when I commit. Appologies for the confusion, still learning.

It could be VS Code or git itself, sometimes it will not let you commit pure whitespace changes.

[tpwrules]

Bindings are kind of expensive, would it be reasonable to instead have an enum and one public function which checks and returns a specific property?

[CallanDaniel]

@tpwrules I don't see why not, this had actually crossed my mind when I was writing the example script. I'll do that. Thanks for the feedback!

[CallanDaniel]

@tpwrules something like this? Yet to do the bindings and a new example script - just wanted to check I'm going in the right direction. EDIT: nevermind - I need a couple days here