Don't show SSID for Wi-Fi calls.

- Delete wifi icon and method to get SSID.
+ Use labels provided by StatusHints instead.

I'm not very happy with the additional "isWifi" cases I ended up
adding in call card fragment.

I felt this was necessary because of assumptions in some cases
that if a label is provided, it should be formatted as a phone
account source. While this was true before, it's becoming less so.
I feel like the fragment shouldn't have to worry about formatting
or choosing the label based on the call and  conditions. It should
just display the label if it thinks it is appropriate to show a
label given the call state.

To fix that, it seems like logic should be moved to the presenter
instead, and possibly to Telephony. But, I'm hesitant to do that
until these WFC changes back merge to master because of potential
merge conflicts and its slightly more risky for this branch,
because it starts dealing with logic/flows outside of WFC..

Bug: 19866988
Change-Id: Iacd5a09259c84ea7be28b0170ae603eb9561f7ca