Fix table column auto-sizing

[emilk]

The bug was that the amount of allocated space was never reported up the Ui chain

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[abey79]

edit: addressed in f46e045

It's still relatively easy to reach a "wrong width situation":

• create a new dataframe view (single row showing since latest-at)
• switch to "Define time range" (often still single row showing since the default PoV component is not the correct one)
• chose a suitable PoV component -> many rows appear, several wrong column sizes

e.g.

This probably makes sense since we salt the table with the schema (which doesn't change between step 2 and 3). Maybe adding the pov component to the salt might be a good idea.

[abey79]

So neat to have well behaving columns!