refactor: implement quick chat state machine

Description

Final MR for implementing state machine in Quick Chat

• Changes have been reviewed and merged into feature branch
• There are new changes to be reviewed, which are broken into two commits
  • aed38ef9: for resolving merge conflicts from !2550 (merged) and !2553 (merged),
  • fbe041d7: fixing issues with sendMessage and clearQuickChat. Details in the comment.

Related Issues

Resolves #1908 (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.

Unit Tests

Manual Testing

Screenshots (if appropriate)

Quick Chat State Machine Walkthrough.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