Add SQL trigger support to v4 model

[lucyzhang929]

More information about SQL Bindings can be found here.

[ejizba]

Added input and output binding support. I'm hesitant to add trigger support while it's still in preview, especially considering users have a workaround with our generic support.

I'd be willing to reconsider if we have users asking for it (upvotes/comments on this issue would be best), otherwise we should be able to do it as soon as it GA's. Feel free to ping us as the GA date approaches