Introduce a slack bot in ACM channels to respond to ACM reported issues

• Find suitable squads to assign the given issue to
• Generate a runbook from a dialogue
• Give a suggestion for the user's question based on ACM docs and code review
• (TODO) Chat with the bot to resolve the issue in complex scenario
  • Access the third system to get more info, e.g. JIRA/support cases/code repo
  • Analyze the must-gather
  • Analyze the user's screenshot/vidoe
  • etc

Code repo: https://github.com/skeeey/acm-troubleshooter/tree/service/slack

Demo: https://drive.google.com/file/d/1KsJiQrhVBVnTpOkS0uv_l9nGFSaZ-KP4/view?usp=sharing

Note: To build a bot, we need a published service that the slack will send HTTP POST requests to this URL when events occur (https://api.slack.com/apis/events-api).