Qt: Conversation and Endpoint dialog performance tweaks.

Qt: Conversation and Endpoint dialog performance tweaks.

Generate column text dynamically. This keeps us from having to iterate
over our tree items each time we receive updates.

Set the uniformRowHeights property.

Stop automatically resizing columns after 200 items.

Fixup name resolution behavior. Disable the checkbox if host name
resolution is disabled.

Change-Id: Ib2fef604d6ee9e39a8b1edd72d58d0cb02d3bb64
Reviewed-on: https://code.wireshark.org/review/16110
Reviewed-by: Gerald Combs <gerald@wireshark.org>
Petri-Dish: Gerald Combs <gerald@wireshark.org>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Anders Broman <a.broman58@gmail.com>