Add apply_dynamic to FuncDecl

[cvick32]

I was running into trouble calling func_decl.apply() with variables of type Dynamic. I tried to iterate over the arguments to get a &[&dyn Ast] by matching up the domain sorts with the arguments, but I felt like having an apply_dynamic function on FuncDecl made more sense.

Let me know if there's an easier way to build &dyn Ast from a Dynamic or if this is redundant/unnecessary.

Here's an example of how I used it:

pub struct FunctionDefinition<'ctx> {
    z3_function: FuncDecl<'ctx>,
    domain: Vec<z3::Sort<'ctx>>,
}
impl<'ctx> FunctionDefinition<'ctx> {
    fn apply(&self, argument_values: Vec<Dynamic<'ctx>>) -> Dynamic<'_> {
        assert!(self.domain.len() == argument_values.len());
        let ref_args = argument_values.iter().collect::<Vec<_>>();
        self.z3_function.apply_dynamic(&ref_args)
    }
}