Code refactoring speed space chart tick Y axis

[flomonster]

Main changes :

1. Iterate on ticks instead of position in speeds.
2. The scale is adapting with the max speed of the chart

This corrects a few problems:

• Axis Y is not visually overloaded even with a top speed of 300km/h
• The Y axis is not visually empty even with a maximum speed of 30km/h
• Having a simplified version of speeds doesn't break everything.

Before

After

[Yohh]

I'm skeptical about removing major lines, the mockup clearly shows them, the only difference is about the max speed to display

did you talk about it with Thibaut?

and if we keep this change, drawMajorGridY() should become drawGridY()

[flomonster]

I'm skeptical about removing major lines, the mockup clearly shows them, the only difference is about the max speed to display

I misinterpreted the mock-up. I'll put the major lines back.

[SharglutDev]

Thank you for the PR, left a few comments

[clarani]

LGTM ✅

[SharglutDev]

Lgtm and tested, nice improvement !