[Bluetooth] Change retrieval of L2CAP features mask

Getting the remote L2CAP features mask is really important, but doing
this as less intrusive as possible is tricky. To play nice with older
systems and Bluetooth qualification testing, the features mask is now
only retrieved in two specific cases and only once per lifetime of an
ACL link.

When trying to establish a L2CAP connection and the remote features mask
is unknown, the L2CAP information request is sent when the ACL link goes
into connected state. This applies only to outgoing connections and also
only for the connection oriented channels.

The second case is when a connection request has been received. In this
case a connection response with the result pending and the information
request will be send. After receiving an information response or if the
timeout gets triggered, the normal connection setup process with security
setup will be initiated.

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>