stack/l2c: Add support for credit based connection oriented channels

This patch adds only support for LE
There is new L2CAP API to create connection and reconfigure connection.
Implementation will always try to create up to 5 channels if possible.

Tag: #feature
Bug: 159786353
Sponsor: jpawlowski@
Test: compile & manual
Change-Id: I8459a7384ca5771b89b6a5c0bdeeacab86dca5da