Investigate supporting new built in Settings Sync

[golf1052]

See user guide here

The main thing blocking this is the release of microsoft/vscode#88309

Some APIs are exposed in vscode.proposed.d.ts but AuthenticationSession is not which blocks any testing at the moment.

This was asked about on Twitter

[golf1052]

Tried to get this working again. Ran into an issue at this line. Didn't try debugging from source.

[golf1052]

Debugged from source, the internal authentication extensions have this in their package.json

"contributes": {
    "authentication": [
        {
            "label": "CodeSync",
            "id": "codesync"
        }
    ]
}

CodeSync now appears in the activity bar UI but doesn't appear in the Settings Sync command dropdown.

[golf1052]

microsoft/vscode#88309 (comment) just closed. This should be possible now.