Merge #490

490: Add MiddlewareChain and StreamingCompiler to runtime r=syrusakbary a=bjfish

It would be nice to add `MiddlewareChain` and `StreamingCompiler` to runtime to be able to use these without having to include the `runtime-core` as a dependency. For example:
```rust
use wasmer_runtime::{MiddlewareChain, StreamingCompiler};
use wasmer_singlepass_backend::ModuleCodeGenerator as SinglePassMCG;
use wasmer_middleware_common::metering::Metering;
let limit = 1_000_000;
let c: StreamingCompiler<SinglePassMCG, _, _, _, _> = StreamingCompiler::new(move || {
    let mut chain = MiddlewareChain::new();
    chain.push(Metering::new(limit));
    chain
});            
wasmer_runtime::compile_with(&prepared_code, &c)
    .map_err(|e| Error::Wasmer(format!("{}", e)))
            chain
        });            
wasmer_runtime::compile_with(&prepared_code, &c)
    .map_err(|e| Error::Wasmer(format!("{}", e)))
```

Co-authored-by: Brandon Fish <[email protected]>

lib/runtime/src/lib.rs

@@ -76,6 +76,7 @@
 //! [`wasmer-clif-backend`]: https://crates.io/crates/wasmer-clif-backend
 //! [`compile_with`]: fn.compile_with.html
 
+pub use wasmer_runtime_core::codegen::{MiddlewareChain, StreamingCompiler};
 pub use wasmer_runtime_core::export::Export;
 pub use wasmer_runtime_core::global::Global;
 pub use wasmer_runtime_core::import::ImportObject;