Data Structure: reduce redundancy when storing fonts

[swissspidy]

Feature Description

This is a follow-up to #12131.

Right now when adding 10 text elements all with the same font, there will be 10 font objects being stored, all with the same information. That's very redundant.

Instead of this, consider storing all existing fonts at the story level instead of on each element to reduce redundancy.

Add data migration.

Alternatives Considered

Additional Context