go/types: unexport Checker.LookupFieldOrMethod

go/types: unexport Checker.LookupFieldOrMethod

Implementation changes in go/types for #6977 required that internal
LookupFieldOrMethod calls had access to the current *Checker. In
order to make quick progress, I added a *Checker receiver to the
function LookupFieldOrMethod (thus making it a method), and added
a new function LookupFieldOrMethod. The plan was always to rename
that function (Checker.LookupFieldOrMethod) such that it wouldn't
be exported; with the obvious name being Checker.lookupFieldOrMethod.
But that name was already in use which is why I postponed the rename.
Eventually I forgot to clean it up. This CL fixes that with the
following renames:

Checker.lookupFieldOrMethod => Checker.rawLookupFieldOrMethod
Checker.LookupFieldOrMethod => Checker.lookupFieldOrMethod

Updates #6977.
Fixes #36916.

Change-Id: Icfafd0de9a19841ba5bd87142730fe7323204491
Reviewed-on: https://go-review.googlesource.com/c/go/+/217134
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Ian Lance Taylor <iant@golang.org>