Allow selecting version when creating PostgreSQL server

[ejizba]

Same as portal:

Probably fine to do as a part of advanced creation

[pamelafox]

This came up today during my VS Code live stream where I showed the creation of PostgreSQL servers. I actually think it's important to do it when creating a server, since you cannot change it after the fact. You have to make a brand new server, dump from the old database, etc. Also, it appears to be defaulting to 12, which is pretty old at this point.