feat(commandline): add :update command to check, download and install Glide updates

[suveshmoza]

#285

• Adds :update command to the commandline to check for Glide updates
• Adds UpdateCompletionSource
• Allows downloading and restarting when an update is available
• Displays real-time update status (checking, downloading, ready, etc.) by updating UpdateCompletionSource based on events emitted by AppUpdater

Testing

• In test environment, Updates are disabled, so added a test case making sure UpdateCompletionSource renders a row with Updates are disabled by policy
• Manually tested the update flow on a debug build

Screen.Recording.2026-03-30.at.03.21.01.mov