* This will be used in certprovider tests where we would want more than one server and client certs.
* Also, updated existing usages of these certs to point to the new files.
* Also copy over the required certs/key files. This avoids the example gomodule from depending on gRPC testdata package which should be able to change independently.
* Fix interop test's SAN.
- For interoperability testing, we need the same certs everywhere.
- This was not possible before because Go could not deal with some field
being encoded as PRINTABLESTRING in the CA and UTF8STRING in the
server1 cert. However, the certs have been fixed in:
https://github.com/grpc/grpc/pull/4096
- Also changed the go root testdata cert to avoid confusion (maybe there
should not be that many copy of the certs in the repo but I will leave
this to the repo maintainers).
