Move Call's histogram reporting code into destructor.

This is for better compatibility with thread annotations and how the
histogram data is collected. In the dtor we can make assumptions about
the state of the object, but that context is lost in member methods
even though they're only called from the destructor (and therefore
thread annotations can't "know" that the object is being destructed
inside those calls).

Bug: webrtc:11993
Change-Id: I8b698cc3340fb0db49430da6f7a9b9a02cabf0c7
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/208200
Reviewed-by: Niels Moller <nisse@webrtc.org>
Commit-Queue: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33295}