feat: implement wasi:http

[rvolosatovs]

Implementation of WebAssembly/wasi-http#162

With Wasmtime binary built from this PR with this patch applied: b007214 (from #60), I have the complete round trip working using components in https://github.com/rvolosatovs/p3-http-test

[rvolosatovs]

cc @pchickey as we just discussed, pushed 926d272, i.e. not porting:

• https://github.com/bytecodealliance/wasmtime/blob/d8360be4c2e9a3730dbd48df0cb2b72e91ca8cbb/crates/wasi-http/src/types_impl.rs#L689
• https://github.com/bytecodealliance/wasmtime/blob/d8360be4c2e9a3730dbd48df0cb2b72e91ca8cbb/crates/wasi-http/src/types.rs#L538
• https://github.com/bytecodealliance/wasmtime/blob/d8360be4c2e9a3730dbd48df0cb2b72e91ca8cbb/crates/wasi-http/src/types_impl.rs#L863

[rvolosatovs]

Added Content-Length handling for outgoing requests and responses in feb9d10, unlike wasip2, we do need to attempt to transmit the request/response to catch the error due to the lack of OutgoingBody::finish.
Since there is no way to report an error on construction of request/response, instead I enforce the fact that Content-Length header set by guests is well-formed.

None of this validation is enforced on requests/responses originating in the host (default HTTP client will enforce that incoming response body is compliant with Content-Length, testing that behavior with Hyper is still TODO) - it is assumed that it is embedders responsibility to ensure that http::Requests they feed to components have well-formed Content-Length header values and their bodies respect that. More concretely, in case of Wasmtime CLI, https://docs.rs/hyper/latest/hyper/index.html is expected to handle Content-Length correctly. From what I can see, that aligns with the existing p2 impl.

cc @pchickey