Part 1 - Add @gitlab/web-ide use behind feature flag

• Part 1 - Add @gitlab/web-ide use behind feature flag
• (Coming soon) Part 2 - Enable user to toggle back to legacy Web IDE

What does this MR do and why?

This MR sets up the integration and usage of our new @gitlab/web-ide package behind a vscode_web_ide feature flag.

Screenshots or screen recordings

• Feature.enable(:vscode_web_ide)
• Visit the Web IDE for any project

• HEADS UP! There's a number of known missing features between this VSCode implementation and the existing Web IDE. This MR is meant to set up the integration of a WIP implementation.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #356595 (closed)