SDP: Serialize sdp connections from profiles/BT APP

This SDP enhancement serialize the sdp reqs and also
same uses same sdp channel when sdp layer receives
multiple sdp req from profiles for same remote.

Thus avoid multiple IOT issues, where IOT remote
goes to bad state when DUT sends more than one
sdp at same time.

Change-Id: Ia7ac9d7254963607f8c9a873d547179c5ebd141d
CRs-Fixed: 2104397
Bug: 246022810
Test: atest net_test_stack_sdp
Tag: #feature