guest traps with "read pointer not aligned"

[rvolosatovs]

On ad4ccf0:

cargo test -p wasmtime-wasi-http 'p3::tests::http_0_3_outbound_request_put' -- --nocapture

fails with:

[guest] construct new request options
[guest] create new stream
[guest] create new future
[guest] construct new request
[guest] set request method
[guest] set request scheme
[guest] set request authority
[guest] set request path and query
[guest] send buffer of 0 bytes...
[guest] buf sent
[guest] write trailers...
[guest] await transmit...
[guest] await handle...
[host] call handle
[host] have built req Request { method: PUT, uri: http://localhost:59133/put, version: HTTP/1.1, headers: {"user-agent": "WASI-HTTP/0.0.1", "content-type": "application/json", "host": "localhost:59133"}, body: () }
[host] contents, trailers
[host] send request..
[host] default send request
[host] connect...
[guest] write trailers done
[host] handshake...
[host] return Ok response
[host] real send request...
[host] await Tx result..
[host] await conn...
[host] conn awaited
[host] write Tx result..
[host] handle return
[host] done writing Tx result
[guest] handle returned
[guest] collect body...
Error: guest trapped

Caused by:
    read pointer not aligned
test p3::tests::http_0_3_outbound_request_put ... FAILED

[dicej]

This fixes it: bytecodealliance/wit-bindgen#1247