classes/go-mod-update-modules: add class to generate module list

classes/go-mod-update-modules: add class to generate module list

Almost entirely based on the create_go.py module for recipetool by
Christian Lindeberg <christian.lindeberg@axis.com>, this instead has the
logic inside a class that can be used to update the list of Go modules
that are used, both SRC_URI and LICENSE.

Integration with devtool upgrade will come shortly, but it needs a bit
more work.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>