From within containers (or possibly other scenarios), the metadata
hostname might not resolve on GCP. Setting this to the full path
guarantees it will resolve.

There is no reason why the client and server factories should be
implementations from the same base.
Doing the cleanup now so that implementation of the #10528 feature will
be less noisy.
Also, re-added tsi to clang-format which was dropped when moved from
src/core/lib to src/core.

If I had a nickle...