Implement structural equality or subtype checking for dynamic component types

Per https://github.com/bytecodealliance/wasmtime/pull/4442#discussion_r928991943 and https://github.com/bytecodealliance/wasmtime/pull/4442#discussion_r928993328, we need to define what it means for two component types to be equal to each other (or more generally, what it means for one to be a subtype of the other) and implement that. See the `PartialEq` impl for `wasmtime::component::types::Handle` for the current, overly-restrictive definition, plus a comment on how it might be improved.