dillon1000/react

[rust] Workspace hygiene

I've primarily used what Cargo calls virtual workspaces, where the top-level 
Cargo.toml just lists a bunch of packages and they each have their own 
dependencies. This is fine, but i've noticed that more repos are using real 
workspaces and they offer a bunch of benefits. You define the dependencies in 
the top-level Cargo.toml and then can easily refer to them from multiple crates, 
ensuring all the versions match up. It makes it easier to refer to other crates 
in the workspace, too, because you define the path once at the root, then every 
other crate can just say `forget_foo = { workspace = true }`. 

I also renamed all the crates to be prefixed with `forget_`, in some cases 
removing the redundant `hir` name, So `hir-optimization` became 
`forget_optimization`, `hir-ssa` became `forget_ssa`. Also note the switch from 
hyphenated names to underscores everywhere, since at the end of the day you have 
to write the name with underscores in source code. 

I also deleted the demo crate that i started with since we don't need it 
anymore. 

And finally, i added an explicit publish = false to all the crates just to 
prevent mistakes.