2934: Show only one tooltip on events' date-icon

[hannaseithe]

Short Description

When hovering over the events' date-icon we show only one tooltip

Proposed Changes

• the problem was that inside EventListItem Component we did not ascribe a unique id to the tooltip
• in order to generate a unique id I hand in the index from the list of events to a singular item, which then can be used to generate a uniqueId
• (the alternative solution of generating a uniqueId from the events._path property I chose not to implement, since we currently do not guarantee that the path is unique (see: #3060)

Side Effects

• ListComponent
• EventsPage
• EventsListItem

Testing

• go to the events page: http://localhost:9000/muenchen/en/events
• hover over DateIcon of an Event Item
  -> check that only one tooltip appears
  -> check that the correct tooltip appears

Resolved Issues

Fixes: #2934

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