### Description
Move store metadata out of source tree. Running Triple-T publisher
always complains about our custom folders (screenshot creator script).
Move everything out of the actual Triple-T metadata folder and symlink
only the necessary ones instead.
### Checklist
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This avoids having hundreds of megabytes of screenshot data in the main repo every single time we re-generate them. Then developers do not have to clone a huge repo (at least if they clone without submodules). It also enables rewriting the screenshot git history to be smaller without rewriting the code git history (which would be quite a bad idea).
