Add voicemail backup/restore columns

BACKED_UP and RESTORED are required for dialer voicemail backup/restore
feature for N MR2. As there are no API bump the fields will be hidden
in NMR2. These fields will be made public in O.

ARCHIVED and IS_OMTP_VOICEMAIL is not used for NMR2, but added in
advance to avoid multiple database upgrades.

IS_OMTP_VOICEMAIL will be used in O to dedupe multiple apps implementing
VisualVoicemailService. All voicemail inserted by the service should
set this field to 1. The UI should only display voicemails with this
field set to 1 when the source_package is also the current active
VisualVoicemailService, as other sources represents the same source of
truth(the carrier) but is outdated.

For example, the query should be
WHERE (is_omtp_voicemail == 0) OR 
(is_omtp_voicemail == 1 AND source_package = "current.vvm.package")

Test: VoicemailProviderTest
Bug: 34463609
Change-Id: I0f3e58fabff2102adf5bc29d81dac46c7e71d410