telephony: introduce a stub SubscriptionController

This is a completely standalone alternative to SubscriptionController
that was replaced with SubscriptionManagerService in commit
c97b4ba2

The reason for this is some older ims packages still need it, as seen
in sargo/bonito ims' getSubId() method:
SubscriptionController.getInstance().getSubIdUsingPhoneId(this.mPhoneId)

The logic behind this implementation is to mock getSubIdUsingPhoneId
method with similar getSubId() method from SubscriptionManagerService
and fit the usage of SubscriptionController in the ims by restoring
getInstance() function as well.

Co-authored-by: EnesSastim <sastimenes@gmail.com>
Change-Id: I1fdd7e00144b76e49ae721d18187ced6467cf28d