[VS Code] Handle chat visibility, loading and focus state

Problem

• Chat needs to be visible only certain conditions - user has access to License, Duo is enabled for project, etc.
• Chat need to be toggled when user runs commands or uses hot keys alt+d
• Chat state needs to behave consistently with the current chat implementation in the VSCode: gain focus when chat is toggled, restore state?,

⚠️ Before implementing, check how Chat state is influenced by the Duo Chat backwards compatibility epic expectations.