Don't form a 'context-independent expr' reference to a member during

Don't form a 'context-independent expr' reference to a member during
name annotation.

Instead, defer forming the member access expression or DeclRefExpr until
we build the use of ClassifyName's result. Just build an
UnresolvedLookupExpr to track the LookupResult until we're ready to
consume it.

This also reverts commit 2f7269b6773de2750f9cd1417ef5f21cd6cf7a91 (other
than its testcase). That change was an attempted workaround for the same
problem.