Revert "Revert deletion of workaround for unordered SEND/RECV "

[YusukeIwaki]

Reverts #32

raw_send was

    payload = JSON.fast_generate(message.compact.merge(id: id))
    @transport.send_text(payload)
    ### handle_message can be called here ###
    request_debug_printer.handle_payload(payload)
    id

    id = @connection.raw_send(message: { sessionId: @session_id, method: method, params: params })
    @callbacks[id] = MessageCallback.new(method: method, promise: promise)

With this implementation, we cannot handle message before raw_send returns the id.
If handle_message is called soon after send_text, it causes unknown id error, because the caller doesn't know the generated id.

So I changed this implementation. id is generated in advance, and raw_send just send text with given id.

    @connection.generate_id do |id|
      @callbacks[id] = Puppeteer::Connection::MessageCallback.new(method: method, promise: promise)
      @connection.raw_send(id: id, message: { sessionId: @session_id, method: method, params: params })
    end