Added APN to string method

There were some limitation of the existing method
ApnSetting.getApnTypesBitmaskFromString, which prints
hipri+default when input is default APN type.

Also added access network type and transport type to string
method.

Test: Telephony sanity tests
Bug: 73659459
Change-Id: I5a24ac4b284c9237f84c8b1a6961569c4f0a747a