feat: add device flow to vscode extension

[benfdking]

• little improvements to the removing and labelling of sessions

[Copilot]

Pull Request Overview

This PR introduces a new device sign-in flow to the VS Code extension along with slight improvements to session management and labelling.

• Added a utility (isCodespaces) to detect Codespaces environments.
• Integrated a new command ("sqlmesh.signinSpecifyFlow") and its corresponding authentication flow.
• Enhanced the authentication provider to support both OAuth and device flow sign-ins.

Reviewed Changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
vscode/extension/src/utilities/isCodespaces.ts	Added a helper function to check for Codespaces environment.
vscode/extension/src/extension.ts	Integrated the new signInSpecifyFlow command.
vscode/extension/src/commands/signinSpecifyFlow.ts	Added a command to allow users to select their sign-in flow.
vscode/extension/src/commands/signin.ts	Updated signIn logic to branch based on environment.
vscode/extension/src/auth/auth.ts	Extended authentication functionality to include device flow.

Files not reviewed (1)

• vscode/extension/package.json: Language not supported