Write a VFS in rust to avoid relying on the JS one

[insipx]

If we write a VFS in rust and compile to webassembly, we can share that pointer with the sqlite to register the VFS and use it. This would be a performance boost since we don't need to cross the JS barrier for storage I/O operations, and would allow us to customize the VFS from rust rather than JS, allowing for more complex operations (maybe encryption, async, etc, allow finer-grained connection management?)

Roy has an extensive index of examples in the wa-sqlite repository, which can be used to model the Rust VFS: Example VFS's