[LVGL+Flow] Spinbox specific properties can be expressions/assignable

[fietser28]

Is your feature request related to a problem? Please describe. I can't dynamically change some of the properties of the spinbox.

Describe the solution you'd like I would like to have the option to set the specific settings of the spinbox to an expression, not just literal. These are the settings that the use of the spinbox doesn't change (expression not assignable).

In my case the spinbox properties need to change when I change to a different mode in my application. As an example I've filled in the expressions I need in the literal fields:

Describe alternatives you've considered

1. Create a fixed spinbox for each mode and swap between these.
2. Keep my current manual implementation in flow/native.

Additional context This has a relation to #229 because spin boxes are mainly useful with encoders (imho).