Interface types don't have concrete method implementations, so it does
not make sense to attempt a lookup.

An interface method would not normally appear in a PGO profile as it has
no symbol in the final binary. However it can appear if the method was
concrete when the profile was collected and it has since been refactored
to an interface method in the code being compiled.

The guards here (OTYPE, !Alias, !IsInterface) now match
noder.linker.relocObj, which does a similar iteration of all methods.

Fixes #67016.

Change-Id: I858c58929c890ac0b2019fbd7c99f683ab63f8bb
Reviewed-on: https://go-review.googlesource.com/c/go/+/581436


LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>