[release-branch.go1.16] runtime: non-strict InlTreeIndex lookup in expandFinalInlineFrame

This is a follow-up to golang.org/cl/301369, which made the same change
in Frames.Next. The same logic applies here: a profile stack may have
been truncated at an invalid PC provided by cgoTraceback.
expandFinalInlineFrame will then try to lookup the inline tree and
crash.

The same fix applies as well: upon encountering a bad PC, simply leave
it as-is and move on.

For #44971
For #45480
Fixes #45482

Change-Id: I2823c67a1f3425466b05384cc6d30f5fc8ee6ddc
Reviewed-on: https://go-review.googlesource.com/c/go/+/309109


Reviewed-by: Michael Knyszek <mknyszek@google.com>
Trust: Michael Pratt <mpratt@google.com>
(cherry picked from commit aad13cbb)
Reviewed-on: https://go-review.googlesource.com/c/go/+/309551


Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>