Allow requests module as QnAMaker's HTTP client

[Zerryth]

Fixes #1187

Description

Properly allow requests to be made and consumed using Python's built-in requests library.

This will allow the option to use an HTTP client that isn't from aiohttp, which may be a sought out option for frameworks that don't wrap their requests in a running "ProactorEventLoop" that's necessary for aiohttp.ClientSession's to work.

For example, using the Quart 13.core-bot sample, it can properly call QnAMaker service with just the following
app.py

import requests

QNAMAKER = QnAMaker(
    endpoint=QnAMakerEndpoint(
        knowledge_base_id=APP.config["QNA_KNOWLEDGEBASE_ID"],
        endpoint_key=APP.config["QNA_ENDPOINT_KEY"],
        host=APP.config["QNA_ENDPOINT_HOST"],
    ),
    http_client=requests
)

Specific Changes

• Configures the request to QnAMaker to the proper shape for the given HTTP client, whether it be aiohttp or requests-based in generate_answer_utils.py and http_request_utils.py
• HttpRequestUtils.execute_http_request method return type goes from aiohttp.ClientResponse -> Any, given that different clients can be passed in to make requests, which return different shapes
• OpenQnAMaker._http_client type from aiohttp.ClientSession to Any
  • Note: we could create an interface instead, I suppose, instead of "Any" type with the requirement that it needs to have a post method, however I'm not sure if this is necessary or not, given that most do (but who knows!)