This is needed as eatt is registering listener in gap nowadays

This patch adds CID to the data path for all the GATT operations.
It also updates unit tests after the change.

The idea for EATT in Mynewt is as follow.
EATT is not exposed to the user i.e. GATT API stays the same. User can
define number of EATT channels supported by the host and it is host
managing those channels.
EATT will be fist choice channel for every ATT operation. In the future
we can make it smarted and make a choice based on the ATT data in the
packet

TODO:
* handle reading and setting client/server Supported features in the
stack instead of eatt code
* add test API to choose channel to use (needed by PTS)

This is initial implementation of handling new GATT opcodes.
Gatt Client supports now:
ATT multi Variable read req
receiving ATT multi notifications

Gatt server supports now:
ATT multi Variable read rsp

In real case, requests are scheduled to be sent after previous one
completes. That happens after response is received. In unittests,
internal API is used for holding pending requests, from which they can
be manually dequeued. Because dequeue operation is always manual and
does not happed after response reception (when will never arrive, there
is no second device) we need to clear flag to be able to start another
procedure.

This is needed to properly handle failed procedure, and pass error to
the app.

This was missing and assert in ble_eatt_l2cap_event_fn was hit

Adds required command and response event.

GATT Client by writing to Client Supported Features characteristic
reports to server what features it supports. These features should be
saved for future use so appropriate subprocedures can be selected.

Channel was taken and function returns before release.

Assert was hit when BLE_ATT_OP_NOTIFY_MULTI_REQ was received.

…config

EATT supported bit is returned when EATT channel number is greater than 0
and Multiple Handle notification based on BLE_ATT_SVR_NOTIFY_MULTI.

For EATT bearer, ATT MTU is same for bot RX and TX and is minimum of the
two. L2CAP Credit Based Reconfigure Request can be used to change its
value.

Added check for link encryption. Removed unused flags for client/server
process. Before processing it is checked if PDU is an ATT one, and
channel is disconnected if not. If after processing PDU next one can't
be received link is discconnected.