Change Request: Splitting enum names based on hyphen and dash for Rust

[RickWinter]

Need to update the design guidelins in rust for the enum naming patterns.

https://github.com/Azure/typespec-rust/pull/247

[heaths]

I could see putting this in implement.md, but this is the idiomatic way of rust already. I already link to the naming docs that say to use PascalCase for types and snake_case for everything else. Do we need to codify those rules separately as well?