[Astetics] Improve Add/remove lane connection icon

[kianzarrin]

From #1485 and #1491. Further improvements to Add/Remove lane connection was proposed:

- render +/- overlay texture inside Lane end circle

- Mouse Icon: without/without pointer ?

- currently we use these cursors

[chameleon-tbn]

• render +/- overlay texture inside Lane end circle with pointer

[originalfoo]

I think only way to know which will work best is to test it - specifically the "overlay inside lane end circle" (I assume that means the larger "circle at end of white lane outline" rather than the tiny circle painted at the end of the lane).