New method that supports CTS test case to check 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: I2918dd7deeb5f400a164295ed201093c7809ca08
2 files changed