dcsctp: Add handover state for stream counts

To allow the transport to be able to know which ranges of
stream identifiers it can be use, the negotiated incoming/inbound
and outgoing/outbound stream counts will be exposed.

This is first added to handover state, with the actual implementation
to follow.

Bug: webrtc:14277
Change-Id: Idd821ecbd8fcb588c88d69f617889318b4b03d43
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/272320
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#37863}

net/dcsctp/public/dcsctp_handover_state.h

@@ -40,6 +40,8 @@ struct DcSctpSocketHandoverState {
     bool partial_reliability = false;
     bool message_interleaving = false;
     bool reconfig = false;
+    uint16_t negotiated_maximum_incoming_streams = 0;
+    uint16_t negotiated_maximum_outgoing_streams = 0;
   };
   Capabilities capabilities;