exekall: Set package attribute when importing submodule
FIX
Set attribute on parent package when importing a module. This allows doing:
# Exekall imports foo.bar itself using something like:
# import_file(module_name='foo.bar', ...)
# Then in another module:
import foo
# This used to raise, as exekall incorrectly did not set "bar"
# attribute on "foo" when importing it.
print(foo.bar)