Add support for non-Stream clients

[jorgenpt]

[danbrakeley]

@jorgenpt This looks good. What do you think about adding this to longtest? I haven't been in this code in a while, but after poking around a bit, I think it wouldn't be too bad. I suspect all you'd need to do is:

1. Adding 2 more perforce servers to test/docker-compose.yaml
2. Expanding the Server type in cmd/longest/server.go to track if this server uses streams or not.
3. Adding Src/Dst entries for these new non-stream servers in the Servers slice at the top of cmd/longtest/main.go.
4. Update setupCommon to create a non-stream depot when appropriate.