Updated throttle behaviour during takeoff

[Georacer]

To include the updates of ArduPilot/ardupilot#27174

[Georacer]

@Hwurzburg I made an effort in updating the documentation of the takeoff throttle.
Feel free to adapt anything to your liking.

[Hwurzburg]

@Georacer questions....what happens with option =1 but no airspeed sensor? that is not addressed here...also at one point you say max thr is imposed until lvl_alt,but also say it isnt for nav takeoffs higher up...whats correct?

[Georacer]

@Hwurzburg I have updated according to the now merged ArduPilot/ardupilot#27758.

what happens with option =1 but no airspeed sensor?
As I write in takoff-mode.rst:
In case more fine-grained throttle control is required, an airspeed sensor must be installed and enabled via the :ref:ARPSD_USE<ARSPD_USE> parameter and :ref:TKOFF_OPTIONS<TKOFF_OPTIONS> bit 0 must be set to 1.

In practice, if one does not have an airspeed sensor enabled, the logic will revert back to TKOFF_OPTIONS=0.

also at one point you say max thr is imposed until lvl_alt,but also say it isnt for nav takeoffs higher up.

With the new TECS PR, TKOFF_LVL_ALT will be used for both TAKEOFF and AUTO modes. I have updated the documentation accordingly.

[Hwurzburg]

@Georacer I made some tweaks....I havent squashed everything yet so you could easily see the changes I made...

[Hwurzburg]

@Georacer George can you resolve thee conflicts and squash and then I will merge, or do you want me to do that?