New hidden API to support the CTS test case that checks the file contents remains unaltered.

Bug: 276402673
Test: atest tests/tests/telephony/current/src/android/telephony/cts/TelephonyManagerTest.java#testCarrierRestrictionStatusAllowList also pformed the sanity and all the basic scenarios are working fine.
Change-Id: I4922b6bf12820e61531782d01dabad55f3b63323