[Settings] Remove MobileNetworkActivity

- remove the component name when launching the intent, using the action intent to replace.

- remove MobileNetworkActivity and rename SubscriptionSettingsActivity as MobileNetworkActivity.

Bug: 210593601
Test: atest
Change-Id: Icb7adaf9f7c7dfe01ff5c133aee8387c1663546c
11 files changed