This reads directly off of the slices rather than ref'ing and unref'ing
them. There's likely some silliness w.r.t. interned slices and
references to them outliving their associated call objects, but we are
just ignoring that for now.

calls/channels

Use it to ensure we don't delete the call from that thread: doing so
would create a cycle that's kind of bad.

setting channel args --draft

clang-format

The clients now block until the channel is in the READY state. This
fixes some test flakiness issues we have had.