"Sign-in with Red Hat" fails in DevSpaces

Description of problem:

It is not currently possible to use "Sign-in with Red Hat" with any extensions that use redhat auth, as provided by vscode-redhat-account One example is OpenShift Toolkit extension. You'll see it tries to redirect to localhost to complete the auth flow, and this of course fails. Given that OpenShift DevSpaces as-a-service already has my Red Hat token, ideally any Red Hat extensions would be able to leverage that token, just like GitHub extensions such as GitHub Pull Requests and Issues are able to grab the user's token you already have from when the user grants permission to the DevSpaces GitHub OAuth application when setting up the workspace.

Prerequisites (if any, like setup, operators/versions):

Steps to Reproduce

1. From https://console.redhat.com/openshift/sandbox Launch RedHat Dev Spaces
2. When you create a workspace, choose Import from Git and specify a private repo URL. Click Create & Open.
3. Authorize Red Hat OpenShift Dev Spaces (Developer Sandbox) to access your GitHub account
4. In your vscode workspace, install the GitHub Pull Requests and Issues extension. You'll need to install 0.76.1 as the latest has an incompatibility with your VSCode version, it seems. Notice that the extension automatically has access to your GitHub account and repo, without completing another auth exchange. This access is by way of the Red Hat OpenShift Dev Spaces (Developer Sandbox) GitHub OAuth application.
5. Now install OpenShift Toolkit extension. 
6. From the Accounts icon in the bottom left, choose "Sign in with Red Hat to use OpenShift Toolkit(1). 

Actual results:

Another browser tab opens to http://localhost:35299/signin which can't be reached.

Expected results:

The extension auths successfully using the Red Hat access token DevSpaces already has for the authenticated user.

Reproducibility (Always/Intermittent/Only Once):

Always

Acceptance criteria: 

Definition of Done:

Build Details:

Additional info (Such as Logs, Screenshots, etc):

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