Dedicated widget for seed control

[quaquel]

As discussed in #2496, having a clean dedicated widget for seed control would be nice. This should allow for controlling the seed and falling back on None (so fully random) if desired.

[nissu99]

can I take this issue?

[EwoutH]

@nissu99 Yes. Two things to watch out for:

• Add Interactive Play Interval Control to Mesa Visualization #2540 is touching the same part of the codebase, which could be cause a merge conflict if you also open a PR. You can either watch till that one is merged, or resolve the conflict when it happens.
• We need to agree on an API / user interface. My proposal is that this seed widget is enabled by default for all SolaraViz models, but I think there were some different ideas on this.