toaster.bbclass: read layer information

In the process of removing the local system
accesses from toaster UI (which must be able to
run remotely), the code to read layer information
is moved from Bitbake Toaster UI
to the server-side toaster.bbclass

    [YOCTO #5604]

Signed-off-by: Alexandru DAMIAN <alexandru.damian@intel.com>
toaster.bbclass: read build stats

In the process of removing the local system
accesses from toaster UI (which must be able to
run remotely), the code to read build stats
is moved from Bitbake Toaster UI
to the server-side toaster.bbclass

The code will accumulate a list of stat files
to be read at build completion. When the
build completes, the whole data list is read and
sent through in a single event.

    [YOCTO #5604]

Signed-off-by: Alexandru DAMIAN <alexandru.damian@intel.com>
toaster.bbclass: read package and image information

In the process of removing the local system accesses
from toaster UI (which must be able to run remotely),
the code to read package information  is moved
from Bitbake Toaster UI to the server-side
toaster.bbclass

     [YOCTO #5604]

Signed-off-by: Alexandru DAMIAN <alexandru.damian@intel.com>