enforce a character limit in PhoneAccountRegistrar for PAs

prevent large character strings in PhoneAccount and PhoneAccountHandle
fields that may cause issues when writing to device. Such fields will
now throw an IllegalArgumentException when the character count is over
the set value.

Test: 4 unit tests
bug: 256819769
Change-Id: Ib54b625c942969873618557e174b0f825e5a5a84