nightly-2024-04-04: chore: simplify how `acvm_backend.wasm` is embedded (#4703)

# Description

## Problem\*

Resolves <!-- Link to GitHub Issue -->

## Summary\*

We only need a single file to be embedded into `bn254_blackbox_solver`
so we don't need the overhead of `rust_embed`. We can instead just
assign the bytes to a const variable.

I've also removed some build dependencies which are unnecessary.


## Additional Context



## Documentation\*

Check one:
- [ ] No documentation needed.
- [ ] Documentation included in this PR.
- [ ] **[For Experimental Features]** Documentation to be submitted in a
separate PR.

# PR Checklist\*

- [ ] I have tested the changes locally.
- [ ] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.