Use .cdn.web-ide.gitlab-static.net to load Web IDE's VSCode workbench in gitlab.com

MR: Isolate Web IDE on separate origin (!185623 - merged)

Description

Instead of loading the Web IDE's VSCode workbench on the same origin as the GitLab instance, load it from the Cloudflare Worker that serves the same Web IDE's VSCode workbench artifact on the origin .cdn.web-ide.gitlab-static.net. This change will ensure that the Web IDE's VSCode workbench can't make authenticated HTTP requests on behalf of the user.

This change depends on completing the issue: Move .cdn.web-ide.gitlab-static.net cloudflare ... (gitlab-web-ide#449 - closed)

Acceptance criteria

• Introduce a web_ide_multi_domain feature flag.
• Use the @gitlab-org/web-ide package version to build the URL's path used to load the correct version of the Web IDE's VSCode workbench.
• In gitlab.com, use .cdn.web-ide.gitlab-static.net to load the Web IDE's VSCode workbench. Control enablement via feature flag.
• Set enablement status the value of the dedicatedWebIDEOrigin feature flag based on the GitLab Rails application feature flag.