Truncate extension descriptions

This is for #8216.

- [ ] Code to toggle between original and truncated description
- [ ] Visual review
- [ ] Code review
These two lines are the ones I am the most unsure about. The easiest way of accessing the shortened version outside of always passing it to `ExtensionManager.toggleDescription()` even if it is not used (but even then that may not be possible) was to store it in the metadata object and conditionally access it in said function.