fix l2cap_reject

fix creation of l2cap channel if hci connection already exists

added l2cap_send_echo_request with fixed sig id

clear ATT and SM protocol handlers on l2cap_init()

don't send encryption command if authentication failed

if both devices support SSP, initiator shall setup unauthenticated link unless connecting to SDP

add security level to l2cap service registration

GAP update to higher security level working

reject l2cap connection if secruity level not reached after auhentication

successfully enable encryption if security level 2 is requested for l2cap service

fix sending of Connection Result - Pending, request authentication if security level isn't enough

request security level 0 for l2cap services

reject connection (0x03 security block) if both have SSP, PSM != SDP, and connection is not ecncrypted

use state_var to store Connection Pending task

send l2cap connection response pending if accept/deny isn't instant

track l2cap channel flush timeout and report in channel open event

store remote flush timeout

added l2cap_le_request_connection_parameter_update

add L2CAP RTX and ERTX timers with 2 secs and 120 secs. defaults

answer request for connectionsless mtu and fixed channels supported in l2cap information request

resend l2cap config request if previous wasn't accepted

added hci_local_bd_addr()

provide missing argument

improved l2cap error handling, better config options validation

log all BTstack command and events