go/types, types2: enable interface inference

go/types, types2: enable interface inference

This CL sets enableInterfaceInference to true.
If problems arise due to this during the freeze, revert this CL.

Fixes #41176.
Fixes #57192.

Change-Id: I881ea6842e9c1101b24d9780323c6af365a40d3e
Reviewed-on: https://go-review.googlesource.com/c/go/+/497657
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>