refactor: quick chat state machines POC

Description

This MR is a POC of introducing State Machine into Quick Chat to simplify the Quick Chat logics by having clear finite states and transitions.

In this MR, only the 'happy path' has been integrated with the State Service. The happy path refers to opening a quick chat, sending a message, and receiving a response.

The diagram below shows the states and state transitions the state service follows.

stateDiagram
  direction TB
  state DocumentStates {
    direction TB
    [*] --> InCurrentDocument
    InCurrentDocument --> InDifferentDocument: switches document
    InDifferentDocument --> InCurrentDocument: returns to original document
[*]    InCurrentDocument
    InDifferentDocument
  }
  [*] --> NoQuickChat: extension initialized
  NoQuickChat --> PendingUserInput: triggers Quick Chat (input box)
  PendingUserInput --> ProcessingRequest: sends message
  PendingUserInput --> NoQuickChat: closes Quick Chat (input box)
  ProcessingRequest --> DisplayingResponse: response received
  DisplayingResponse --> PendingUserInput:  triggers Quick Chat (input box)
  DisplayingResponse --> QuickChatCollapsed: collapses chat
  QuickChatCollapsed --> DisplayingResponse: expands chat
  DisplayingResponse --> DisplayingResponse: sends special command
  DisplayingResponse --> ProcessingRequest: sends message (thread comment)
  ProcessingRequest --> Error:network error/timeout
  Error --> ProcessingRequest: sends message (thread comment)
  Error --> PendingUserInput:  triggers Quick Chat (input box)

Related Issues

#1831 (closed)

How has this been tested?

• If src/browser or src/common has been modified, please consider interoperability with the Web IDE. See Running the Extension in WebIDE.
• Consider an end-to-end test for significant new features that aren't covered by integration tests.

Run the extension locally

1. select a block of codes
2. press option + c to open Quick Chat prompt
3. Type explain and hit enter
4. A comment thread is created and the response is streamed.

You can also check the status transitioning accordingly in the output panel > GitLab Workflow

Screenshots (if appropriate)

State Machines Shadowing Quick Chat.mov

What CHANGELOG entry will this MR create?

• fix: Bug fix fixes - a user-facing issue in production - included in changelog
• feature: New feature - a user-facing change which adds functionality - included in changelog
• BREAKING CHANGE: (fix or feature that would cause existing functionality to change) - should bump major version, mentioned in the changelog
• None - other non-user-facing changes