gtk+3: add PACKAGECONFIG for libcloudservice and tracker; fix cups backend

gtk+3: add PACKAGECONFIG for libcloudservice and tracker; fix cups backend

Add options to enable support for libcloudprovider and tracker

If the cups backend is enabled, the mandatory file backend gets disabled and
thus configure fails. Fix it by not defining the print-backend and just include cups
as a dependency. Additionally add it as a runtime dependency.

Now, if cups gets enabled, it should include the following print-backends
by default: cups,lpr,file

Signed-off-by: Markus Volk <f_l_k@t-online.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>