Go 1.23 changed how go/types handles type aliases, which breaks code
generation if you use a package that has an alias type (example:
https://pkg.go.dev/github.com/golang/[email protected]/ptypes/timestamp#Timestamp
). These were getting generated as just the unqualified name, without
the package. If you used a previous version of Go, it meant that if that
aliased type was in an internal package we'd try to import the internal
package instead, resulting in a compilation error.

Add a switch to handle that case, and bump the go.mod version to support
using types.Alias.