L2CAP Integrate channel mode in configuration

Store the channel retransmission and flow control mode requirement from
user.

Enable ERTM mode when specified in channel registration and connection
request from client.

Add the first POC for sending I-Frame.

FCS is not supported yet.

Bug: 144770885
Test: run_cert.sh and bluetooth_test_gd
Change-Id: I4a6f01ad31573e18546134007a1e95cb5f2d215b