Provide marginally better debug information for client side auth problems

Move parent removal from final destruction to destruction request 

Add a document describing a server reflection protocol.

This is largely cribbed from @dklempner's original PR (#2744) . Taking over as he is out on vacation. Removed the discussion around host-reflection and corresponding uses of `host` from the API.

Naming design document

Testing port server

Add ObjC helpers to use OAuth2

We don't need the list for cancel propagation after that point, and
doing it early avoids a bug whereby the call is reffed after reaching a
zero ref when the parent is destroyed first.

Server creds auth md processor

Channel state api

Only slow down tracing tests if stdout isatty

Reduce mac CI load

Document finish

Require very explicit registration of non-SSL hosts in Objective-C.

Fix memory leaks

Re-enabling tests that got culled off.