Allow other labels in sending to process

[edescourtis]

swarm/lib/swarm/tracker/tracker.ex

Line 699 in 7d2c2f4

case GenServer.call(pid, {:swarm, :begin_handoff}) do

I am using a library which is intercepting GenServer.call and GenServer.cast below my module. Something fairly common in the OTP world. I need an option to tell Swarm to send calls using a specific label to get around this issue. See https://github.com/blackberry/Erlang-OTP/blob/3ec06ce97019eed9472a2cf8950ed23d7a2e6b9b/lib/stdlib/src/gen.erl#L146 .
Can we please add this option when registering the process?

[edescourtis]

default can be :'$gen_call'
https://github.com/blackberry/Erlang-OTP/blob/3ec06ce97019eed9472a2cf8950ed23d7a2e6b9b/lib/stdlib/src/gen_server.erl#L175

[edescourtis]

Another option would be to provide a call function reference (would be acceptable)