Auth: add offline mode support for Ollama models

[abeatrix]

CLOSE https://linear.app/sourcegraph/issue/CODY-2631/cody-requires-an-online-connection-and-an-open-vs-code-to-work-offline

This change adds support for an offline mode that allows users to only use Ollama models with Cody without the internet.

The key changes are:

• Added a new offlineModeAuthStatus object to represent the auth status in offline mode
• Updated the SimpleChatPanelProvider and AuthProvider to handle the 'offline' auth kind
• Modified the newAuthStatus function to return the offline mode auth status if isOfflineMode is true
• Updated the syncModels function to handle the offline mode case and not sync models
• Added a new "Use Cody Offline with Ollama" button on the Connection Issues page

The screen below only shows up when there is a networking issue, e.g. when Cody does not have internet connection:

TO-DO

• Add tests for offline mode?

Test plan

1. Start Cody from this branch
2. Open Ollama
3. Open Chat and ask Cody a question to verify Cody still works when there is an Internet connection
4. Turn off your Wi-Fi settings
5. Reload VS Code
6. Verify you are seeing the connection issue page
7. Click on Use Cody Offline with Ollama
8. Verify the sidebar is loaded correctly
9. Open Chat and select an Ollama instruct model
10. Ask Cody a question and verify you are getting a response back from the Ollama model

Demo

[sqs]

reviewing