Upload should inline the Wasm

When specifying the `--wasm-path` of the contract, the new method `fn upload` will be generated. It will use `include_bytes!(wasm_path)` which includes bytes of the contract. It's very fragile since it requires that at the time of calling the `ink-wrapper`, the `--wasm-path /path/to/wasm/file` is correct with regards to where it will be used, not where it's currently called from. I.e. the relative path to the Wasm file MUST be specified for the call time, not generation time. See https://github.com/Cardinal-Cryptography/ink-wrapper/blob/aleph-client-compat/Makefile#L38-L50 for example how this path changes.

Instead, we could simply inline the whole body of the contract as an array in the same file as the wrappers. Or, alternatively, inline it in a separate file but output it alongside the wrapper and call `include_bytes!` on it.