ScalaPBModule does not generate code for third party proto files

[a-morales]

If a dependency has Proto files, but doesn't have implementations for them, then compilation fails. The ScalaPB module does have a setting to search for Proto files in dependencies, but it only generates for files defined here

mill/contrib/scalapblib/src/mill/contrib/scalapblib/ScalaPBModule.scala

Lines 55 to 57 in 4540af4

	def scalaPBSources: T[Seq[PathRef]] = Task.Sources {
	moduleDir / "protobuf"
	}

The scalaPB sbt plugin has options to support this as documented here https://scalapb.github.io/docs/third-party-protos.