Add web_ide_language_server flag

Issue: Add "web_ide_language_server" feature flag in m... (#479551 - closed)

What does this MR do and why?

This MR contains the following changes:

• Introduces a new feature flag: web_ide_language_server. Its value is passed to the Web IDE config.
• Bumps Web IDE version to include changes that allows passing the flag to the GitLab Workflow extension.

References

Issue: Add "web_ide_language_server" feature flag in m... (#479551 - closed)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Flag value	Recording
Disabled	disabled.mov
Enabled	enabled.mov

How to set up and validate locally

• Pull this branch and run yarn install
• Visit https://gdk.test:3443/rails/features/ and search web_ide_language_server flag. Use the toggle button to control enablement.
• Open a project in the Web IDE.
• Open the Command Palette, search for User Settings and search for gitlab.featureFlags.languageServerWebIde .
• Observe flag value matches checkbox value.