feature: flow default input values taken from script default values

[jhygate]

Script input values are really nicely pre-populated! I love that the default values set in main for python scripts pre-populates the default input values.

It would be really useful if when setting the inputs for a flow to a script input (e.g. by using Copy input's schema from first step) the default values were set to match the scripts default values

I imagine this could be done by auto-populating the default sections in the script .yaml and using that to populate the input defaults .yaml for the flow