Make generated code `gofmt` compliant.

[ajnavarro]

Generated code doesn't pass gofmt.

[guseggert]

Is this worth doing vs. running gofmt after generating code? Getting e.g. the import statement order correct doesn't seem worth doing.

[ajnavarro]

I think it is straightforward enough, it can be done programmatically: https://pkg.go.dev/go/format#Source