libcamera: Improve Request life cycle tracking

The current logging to track the status of a Request when running the
Android camera HAL provide the following information:

When a Request is queued to libcamera:
HAL camera_device.cpp:1776 '\_SB_.PCI0.I2C2.CAM0': Queueing Request to libcamera with 1 HAL streams

When a Request completes:
Request request.cpp:268 Request has completed - cookie: 138508601719648

The queueing of a Request reports the number of streams it contains
while the completion of a Request reports the address of the associated
cookie.

This makes very hard to keep track of what Requests have completed, as
the logging associated with a queue/complete event does not allow to identify
a Request easily.

Add two more printouts to make it easier to track a Request life cycle.
To make it possible to print the Request cookie in the CameraDevice
class add a method to access it from the CameraRequest class.

The result looks like the following trace:

Request request.cpp:92 Created request - cookie: 140701719392768
HAL camera_device.cpp:1710 '\_SB_.PCI0.I2C2.CAM0': Queueing request 140701719392768 with 1 streams
HAL camera_device.cpp:1747 '\_SB_.PCI0.I2C2.CAM0': 0 - (4160x3104)[0x00000023] -> (4160x3104)[NV12] (direct)
...
Request request.cpp:268 Request has completed - cookie: 140701719392768
HAL camera_device.cpp:1800 '\_SB_.PCI0.I2C2.CAM0': Request 140701719392768 completed with 1 streams..

Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>

src/libcamera/request.cpp

@@ -88,6 +88,8 @@ Request::Request(Camera *camera, uint64_t cookie)
 	metadata_ = new ControlList(controls::controls);
 
 	LIBCAMERA_TRACEPOINT(request_construct, this);
+
+	LOG(Request, Debug) << "Created request - cookie: " << cookie_;
 }
 
 Request::~Request()