Return a better status and message for a collective broadcast group with no

send ops.

Before this change, if we create a group of collective ops comprising only
broadcast_recv, we would trigger a check failure with the message: "Check
failed: ir->source_rank >= 0 (-1 vs. 0)".  After this change, if a user creates
a collective group without a broadcast_send they should see a better error
message.

In the process, we remove the check and put error message in the status of
collective param initialization.

PiperOrigin-RevId: 220332905