We've been treating the `seq` attribute incorrectly in lldb-dap.
Previously, we always had `seq=0` for events and responses. We only
filled in the `seq` field on reverse requests.
However, looking at the spec and other DAP implementations, we are
supposed to fill in the `seq` field for each request we send to the DAP
client.
I've updated our usage to fill in `seq` in `DAP::Send` so that all
events/requests/responses have a properly filled `seq` value.
e29d4ebb89