Remove the uniffi-rs project

We build an old uniffi-rs version (0.7.0) and we consume it only in Application Services.

However, I've tried to build AS without it (only AS for now, not a full build) and I managed to build it. Please notice that AS includes a more recent uniffi-rs in its Cargo vendor archive, so I think the one we provide isn't used at all.

We used to have a patch for reproducibility, but it was upstreamed a while ago.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information