`Return(ResultType)` + `Meta("struct:pkg:path", "path")` leads to some broken return types in gen/**/service.go.

[bkeane]

As seen

When generating methods where the Result is a ResultType, and Meta is being used to declare alternative package pathing, some return type signatures in generated code do not reflect this package.

Somewhat related to #3546

Repro Design

package design

import (
	. "goa.design/goa/v3/dsl"
)

var _ = Service("Repro", func() {
	Method("row", func() {
		Result(Row)
		HTTP(func() { GET("/") })
	})
})

var Row = ResultType("application/vnd.goa.row", "Row", func() {
	Attributes(func() {
		Field(0, "id", String, "An ID field")
	})

	Meta("struct:pkg:path", "types")
})

[bkeane]

#3553

Fixed by