This commit implements an initial WASI C API that can be used to instantiate
and configure a WASI instance from C.
This also implements a `WasiBuilder` for the C# API enabling .NET hosts to bind
to Wasmtime's WASI implementation.
* Move the C API to a separate crate
This commit moves the C API from `crates/api/src/wasm.rs` to
`crates/capi/src/lib.rs` to be located in a separate crate. There's a
number of reasons for this:
* When a Rust program depends on the `wasmtime` crate, there's no need
to compile in the C API.
* This should improve compile times of the `wasmtime` crate since it's
not producing artifacts which aren't always used.
* The development of the C API can be guaranteed to only use the public
API of the `wasmtime` crate itself.
Some CI pieces are tweaked and this overall shouldn't have much impact
on users, it's intended that it's a cleanup/speedup for developers!
* Disable rustdoc/tests for capi
* Review feedback
* Add back in accidentally deleted comment
* More renamings
* Try to fix dotnet build
