Implement API to retrieve carrier configs as needed

Implement API CarrierConfigManager#getConfig[ForSubId]
to retrieve carrier config as needed.

Bug: 244087782
Test: CarrierConfigManagerTest
Merged-In: Iead17ed4b6db73b2bb87d1e752c3348caa0d1cde
Change-Id: Iead17ed4b6db73b2bb87d1e752c3348caa0d1cde
(cherry picked from commit 14757c25352e16ebe2e2f321c276a3b408763eec)
1 file changed