Migrate set network selection auto from legacy subscription

In the legacy subscription flow, upon SIM loaded, if the slot mapping
changed, a set network selection auto mode request will be sent to
modem. Migrate that logic to the existing flow.

Fix: 278517596
Test: voice call + internet browsing + reporter verified fix
Change-Id: If54767be505aaaa7c11c33ddb96feaa42cb8ef99