toaster: Remove compatible_layerversions() method

toaster: Remove compatible_layerversions() method

Remove compatible_layerversions() and replace calls to it with
calls to get_all_compatible_layer_versions().

The sorting done in compatible_layerversions() is not relevant,
and the code can be simplified by using get_all_compatible_layer_versions().

[YOCTO #8364]

Signed-off-by: Elliot Smith <elliot.smith@intel.com>
Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: brian avery <avery.brian@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>