Add product-services.img for `fastboot flashall`.

This CL is largely and adaptation of
Ifd119650dd3316508870df0dfc770099e95ae1d1

Bug: 80741439
Test: Successfully built product-services.img with one module in it, and
flashed on device. Also successfully built image with
/system/product-services and no dedicated /product-services partition.

Change-Id: I204a831e052d018018ab124d70ad1ff1610ee007