Add CitationKey as a default column (#10510)

[suftware]

Added CitationKey as a default column to the entry table by adding it to the default preferences. This closes #10510.

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[calixtus]

I don't like the base issue and the premise, because even if our focus is bibtex, even the heavy bibtex users dont need this column all the time and introducing it is just 4 clicks away.

But.

Decisions have been made and the change looks good to me. So I approve. Thank you.