Added a field to track if the call is to a voicemail instance.

Refactored common code between CallerInfo and CallerInfoAsyncQuery that deal
with voicemail number comparison.

In CallerInfo.java added a new field mIsVoiceMail to indicate this is a
voicemail call.
Added a new method to convert the CallerInfo into a VM instance.
Added a new method to generate a debug string from an instance.

PhoneNumberUtils has a new method "isVoiceMailNumber" to check if a number
is a VM one. I left the method as hidden. Previously any security exception
failure was cached in a static variable. I removed that and
privilege the optmistic scenario. I am not sure if the security exception
is only for the 'regular' telephony layer and if it applies if a 3rd party
VM app is installed (e.g googlevoice), hence i removed the cashing to make
sure we can pick up new voicemail providers when installed/enabled/disabled.

Bug:2112640