DialerStats: track how frequently contact images are present on the call detail page

For retail devices (and installer builds), introduce tags to be read
by a separate, additional, package.

This will not be read or collected in any community (nightly/M/etc) or
self-built build.

Change-Id: Ic06b09eb4667297abd44aa11b504088a91cd5102
(cherry picked from commit d6e4f35eaa215d6e91400f749d9c92d57a16a7d6)