[rviz_tactile_plugin] False impression of missing data with "no recent msg" status

[guihomework]

Customers reported thinking their software producing contact_states was broken, when the rviz_tactile_plugin contact_state displays reported "no recent msg" for some contact_states.

However, it is possible that some group of taxels do not produce a contact_state, just because their tactile values are negative (until #8 is considered) or zero. This is fine and not an error, so not worth a warning.

Currently the timeout and the time of the last seen message is considered, forever. So the "no recent msg" never disappears if no new message is published for a certain group of contacts.
https://github.com/ubi-agni/tactile_toolbox/blob/melodic-devel/rviz_tactile_plugins/src/tactile_contact_display.cpp#L246

Maybe some "forgetting" about past contact_states could help ? a sort of second timeout, of 5 seconds or so, to make the contact disappear 5 seconds after the user selected timeout, while keeping the force display to be invisible directly after user selected timeout.