change of inkstroke modeler

[Doublonmousse]

On the rnote side :

• cargo.toml change (for now using a custom branch/fork of the inkstroke modeler)
• API change (usize for n_steps, no PredictionParams and no tilt or orientation)

On the inkstroke modeler side

• rewrite to rust of the logic This rewrite is mostly to have something that's easier to build/compile from rust on all platforms.

[Doublonmousse]

Uh now I have issues when I pause the stroke and continue moving later.

Edit : fixed

[flxzt]

Tested on my X1-Yoga and my desktop PC and I have found no issues or differences in behaviour to pre-rewrite.

Looks good to me!