Rework figure eight init

[KonradRudin]

Solved Problem

When the figure eight direction is changed, the vehicle flies strange pattern sometimes performing several strong turns in different directions resulting in the camera needing to pan a lot before tracking a new object reliably again.

Fixes #{Github issue ID}

Solution

• Reworke the figure of eight initialization logic such that it initialize to a segment where less maneuvering is necessary.

Showcases of improved performance. As test the figure of eight orientation is just changed (to simulate a worst case scenario when the POI is changed from one side to the opposite side)
On current main apply new figure eight when on a circle

After fixes

On current main apply new figure eight when on a straight line segment

After fixes

[sfuhrer]

Has this already been flight tested? Could you add some screen recordings if you have something that helps understanding the problem?

[RomanBapst]

@KonradRudin MINIMUM_MINOR_TO_MAJOR_AXIS_SCALE is unused I think

[RomanBapst]

@KonradRudin Looks very clean in general! I did not go through the maths completely, but I think I understood what the code is doing.
A simple unit tests that checks for proper initialisation would be nice but no blocker.

[KonradRudin]

@sfuhrer i still wait for our test flight to test this, more prio work for now. I will attach when i have the logs

[KonradRudin]

@RomanBapst I made the renaming fixes. And i added again a new (and hopefully even better initialization. Can you check again?

[KonradRudin]

@sfuhrer I have already added some cases in the description, which should be better with the new initialization. The goal is to reduce the tight turns, and also avoid first turning in one direction, followed by another turn in the different direction. This was even worse in real flights with strong wind

[KonradRudin]

@sfuhrer Here is the log of a flight test. https://review.px4.io/plot_app?log=82df7927-e6b1-47eb-9420-a471df09f049
Flight tests looks smoother with the initialization than before, there are less turns involved then prior.

[sfuhrer]

Thanks for providing the context!