Add UCS-2 support for SimPhonebookContract

This simplifies the API by eliminating the need to attempt to detect
and report unsupported characters.

Test: atest FrameworksTelephonyTests:com.android.internal.telephony.uicc.IccUtilsTest TeleServiceTests:SimPhonebookProviderTest
Bug: 154363919
Change-Id: Ica8f3a642ee50ca81c43822ba39c0a071c279705