Add USSD codes over IMS feature

Normally, USSD codes is sent over the CS pipe. However if CS is out of
service, it should send USSD codes over IMS instead.

Change as follows:
- Change to allow using ImsPhone when dial USSD codes even if
  UT is disabled.
- Adds implementation to send USSD via ImsPhone.
- If does not support to send USSD via ImsPhone due to modem
  limitations, it will send over the CS pipe instead.

Test: atest GsmCdmaPhoneTest, atest ImsPhoneTest
Bug: 141350403
Change-Id: If6cf5bd5627021b06f75c798d58b9906362896b7