A major cleanup, disentangling net_if and ssl_if.
Pulled a lot of common logic into the core and reduced size of net_if implementations.
CL: Mongoose net_if and ssl_if refactoring
PUBLISHED_FROM=29bd4dcb264a1fd96b3dd164e2d880e1c2c0921e
In certain files it was necessary to make tests work from public
mongoose repo, so this commit makes things consistent.
PUBLISHED_FROM=694454d0ff007229c65d524a2a2beaf126420f15