Add tests for LocalFunctionStatementSyntaxWrapper

[sharwell]

This wrapper type was added in #2370 without tests. It's not too difficult to add them; see commit c31beae and other examples from that pull request for how to implement good coverage of these types.

[bjornhellander]

I can have a look at this

[sharwell]

@bjornhellander Maybe start with #2376 (a simpler case) and then do this one? I won't stop you if you start with this though. 😆

[bjornhellander]

😄 Yes, I just randomly picked one and I see that there are smaller ones available, so I'll have a look at some other wrappers first and come back to this soon. You can keep it assigned to me for now if you want.