Enable update checks and allow auto-updates

[timtmok]

Release Notes

Address #1837

Enables update checking by default. The update service will respect the update mode setting. When an update is discovered, an action is available for the user to download the update.

An auto-update option is shown for Mac and Windows users that is off by default. Turning on auto-updates will check the pre-releases for a new version. This will update Positron in the background.

If auto-update is enabled in dev, it disables updates. The check has been moved later in the initialization so that the logs can show the preferences were set. Disabling auto-update will allow update checks for testing.

When auto-updates off, the download update action links to the file update instead of the Positron site. This ensures the correct update is downloaded in case there is a lag with updating the website download links. The Positron website has also been added to the trusted links.

New Features

• Releases: Positron should check for updates #1837 Update checking is enabled by default. There are preferences for setting when updates are checked or to turn it off. A preference for auto-updates has been added to Mac and Windows that is disabled by default. Turning it on allows Positron to immediately download the update.

Bug Fixes

• N/A

QA Notes

[github-actions]

E2E Tests 🚀
This PR will run tests tagged with: @:critical

^{readme  valid tags}

[jmcphers]

LGTM, will be great to have this turned on!