Support x-go-type-skip-optional-pointer in client query

[TelpeNight]

Hello.
We've tried to use x-go-type-skip-optional-pointer with optional slices in our code base. But generated client code became invalid. Original template makes dereference of pure slice.
I've added an extra check for this case, for query parameters. Other param locations may need the same check.
Note, that supporting optional not-nilable types (ex int) with x-go-type-skip-optional-pointer requires extra work. As if params.{{.GoName}} != nil check will not compile. But zero value semantic is not well defined in this case.

[jamietanna]

Thanks for this - will try and look at it once the backlog of items for v2.4.0 are down!