* Refactor the internals of `Store<T>`
This commit is an overdue refactoring and renaming of some internals of
the `Store` type in Wasmtime. The actual implementation of `Store<T>`
has evolved from the original implementation to the point where some of
the aspects of how things are structured no longer makes sense. There's
also always been a lot of unnecessary gymnastics when trying to get
access to various store pieces depending on where you are in `wasmtime`.
This refactoring aims to simplify all this and make the internals much
easier to read/write. The following changes were made:
* The `StoreOpaque<'_>` type is deleted, along with the `opaque()`
method.
* The `StoreInnermost` type was renamed to `StoreOpaque`.
`StoreOpaque<'_>` is dead. Long live `StoreOpaque`. This renaming
and a few small tweaks means that this type now suffices for all
consumers.
* The `AsContextMut` and `AsContext` traits are now implemented for
`StoreInner<T>`.
These changes, while subtly small, help clean up a lot of the internals
of `wasmtime`. There's a lot less verbose `&mut
store.as_context_mut().opaque()` now. Additionally many methods can
simply start with `let store = store.as_context_mut().0;` and use things
internally. One of the nicer aspects of using references directly is
that the compiler automatically reborrows references as necessary
meaning there's lots of less manual reborrowing.
The main motivation for this change was actually somewhat roundabout
where I found that when `StoreOpaque<'_>` was being captured in closures
and iterators it's 3 pointers wide which is a lot of data to move
around. Now things capture over `&mut StoreOpaque` which is just one
nice and small pointer to move around. In any case though I've long
wanted to revisit the design of these internals to improve the
ergonomics. It's not expected that this change alone will really have
all that much impact on the performance of `wasmtime`.
Finally a doc comment was added to `store.rs` to try to explain all the
`Store`-related types since there are a nontrivial amount.
* Rustfmt
ca3947911e