Generating empty Dispatch and GlobalDispatch implementations for each interface in wayland-rs

[mattkae]

What's new?

• Implemented write_dispatch_rs which writes the Dispatch and GlobalDispatch implementations for each Wayland interface to src/dispatch.rs
• The generated code contains no-ops for each incoming request as well as a generic data binding function
• Updated the protocol parser to check whether or not an interface is global so that we can properly generate the GlobalDispatch implementation
• Simplified how metadata is handled for the WaylandProtocol objects by removing the tuple

How to test

1. Run cargo build
2. See that src/dispatch.rs gets generated with a bunch of no-op implementations

Checklist

• Tests added and pass
• Adequate documentation added
• (optional) Added Screenshots or videos