[dev.regabi] cmd/compile/internal/types: add pos/sym/typ params to NewField

These are almost always set, so might as well expect callers to
provide them. They're also all required by go/types's corresponding
New{Field,Func,Param,Var} functions, so this eases API compatibility.

Passes toolstash-check.

Change-Id: Ib3fa355d4961243cd285b41915e87652ae2c22f6
Reviewed-on: https://go-review.googlesource.com/c/go/+/272386


Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Robert Griesemer <gri@golang.org>