Importing raw camera photos

A partial implementation in #2106 but is blocked. This is the final deliverable from a Google Summer of Code [project](https://graphite.rs/volunteer/guide/student-projects/#2024-raw-photograph-decoding-in-rust).

This work was stalled because it was unusable due to memory restrictions #1895.

This will be solved by reducing copying of image data as much as possible via the asset database system (#1604). Further, we can save the actual data in JS memory and read it from Wasm memory.

Other possible solutions:
- [x] Reducing copying of image data using `Arc`.
- [ ] Using [memory64](https://github.com/WebAssembly/memory64/blob/main/proposals/memory64/Overview.md) if it is released as stable in Chrome, Firefox, and Safari.
- [x] Somehow reducing the memory requirements of autosave (e.g. don't encode the uncompressed f32 values as base64). Possibly addressed as part of #1604.