Rename ComponentInterface?

[bendk]

I feel like this name is pretty opaque, unless you know about the history of UniFFI and the Mozilla Rust Components strategy. It's docstring says it's the "main public API", so we should have a nice name for it.

Maybe we could name it something like CrateInterface, LibraryInterface, ModuleInterface. I see people using these terms more often than "Component" to describe the thing they're using UniFFI to generate bindings for. CrateInterface doesn't have a great ring to it, but it makes it clear that it's handling 1 crate in a multi-crate setup.

Maybe we could lean into compiler terminology and call it an "IR", since it's an intermediate representation between the Rust code and the generated bindings.

We could also keep it ComponentInterface. Is this something that's confused/bothered others, or is it just me?