This commit fixes the `wasmtime::Instance` instantiation API when imports have the same name but might be imported under different types. This is handled in the API by listing imports as a list instead of as a name map, but they were interpreted as a name map under the hood causing collisions. This commit now keeps track of the index used to define each import, and the index is passed through in the `Resolver`. Existing implementaitons of `Resolver` all ignore this, but the API now uses it exclusivley to match up `Extern` definitions to imports.
This is the wasmtime-jit crate, which contains JIT-based execution
for wasm, using the wasm ABI defined by wasmtime-environ and the
runtime support provided by wasmtime-runtime.