Cleanup chat boxing

[Twister915]

The Chat type is defined to have a Vec<BoxedChat> as a member (indirectly, through BaseChatComponent type) because originally I thought the indirection was necessary in Vec type. As it turns out, I didn't know Rust all that well when I wrote this code, and I realize now that we don't need the indirection in this case.

I left the BoxedChat alias and the .boxed() method on the Chat type because indirection is required in one case (the only associated value for ChatHoverEvent::ShowText must be a Chat type).

Review Notes:

• Are we OK to make this sort of change without bumping to 0.3.0? I don't think this'll break any usages of the library.

[Ichbinjoe]

I think you are right in asserting that this shouldn't break most occurrences of this library (due to auto-dereferencing), but this will break anyone trying to unwrap the box (because spoiler, no box to unwrap).

Approving because I'm going to assume you are the only real user of this library, and if you aren't, sorry to the person who is using this as well as doing weird boxy things with their chat.

[jaecam]

Yeah, the indirection is required for that hover event enum variant.
Not sure the BoxedChat alias is adding much value, but I can mostly get behind the boxed method from a code style POV. May want to also consider moving the point of indirection (which field is boxed), to increase cache locality (though there's currently no use of these types in craftio as far as I can see, so such an optimization is likely premature.)