TimeseriesView: Make it possible to see the values under the playback head

[linear[bot]]

Problem

When the playback head is over a datapoint in the timeseries graph, it's very difficult to get the actual data value because the scrubber handle gets in the way.

You can see in the video below how the cursor turns into <-|-> to direct the user in dragging the timeline bar around.

hover.mov

Solution/requirements

Prefer the tooltip over the cursor changes. This means that when the cursor is within the activation distance* of any point, use the tooltip instead of a cursor.

*activation distance = the typical distance within which the tooltip appears

[Wumpf]

@emilk still a problem for me on latest main. You've looked at the wrong thing? The problem here is that in the time series view (not the timelien) hovering a series doesn't give you any information if the playback line is in the way