rust/CI: Enables networking support

Enables networking support and network device drivers support
required by net_device wrappers introduced in RFC for dummy_rs driver.

Specifically, this change, enables the following configuration options:

- CONFIG_NET,
- CONFIG_NET_CORE,
- CONFIG_NETDEVICES.

Configs generated from 5.14.0-rc1.

Signed-off-by: Dariusz Sosnowski <dsosnowski@dsosnowski.pl>
Signed-off-by: Finn Behrens <me@kloenk.de>

Author: sodar