ProtoContextSecundus

A common context used between Quill and ProtoQuill. This is more like a pre-context because the actual run methods cannot be contained here since they use macros. Right now not all Scala2-Quill context extend this context but hopefully they will all in the future. This will establish a common general-api that Quill contexts can use. In ProtoQuill, this context is used for the base of all other context and allows the Scala 3 macros to call the execute___ methods. In Scala2-Quill wherein macros are less strict about signatures, this cannot be used for Context (in Context.scala) but various higher-level context extend it as a guard-rail against API drift i.e. so that the Scala2-Quill and ProtoQuill internal-context APIs remain largely the same.