Cannot parse ARC4 Struct that use the `kw_only` flag

[CiottiGiorgio]

The unit testing framework errors out when parsing arc4.Struct that use the kw_only boolean argument.

Steps to replicate:

• Render the current python SC template.
• Create a new type in the hello_world contract:

class ExampleStruct(arc4.Struct, kw_only=False):
    a: arc4.UInt64
    b: arc4.String

• algokit project run test

This fails for kw_only=True and kw_only=False.

#23 is the working PR to fix this.