FE for vscode extension marketplace settings

Issue: Extensions Marketplace settings UI (#508988 - closed)

What does this MR do and why?

FE for vscode extension marketplace settings

• Also introduces a vscode_extension_marketplace_enabled jsonb accessor that wraps the vscode_extension_marketplace field.
• This is because the UX design have the enablement toggle working independently.

Screenshots or screen recordings

Designs: https://www.figma.com/design/2DWZOSQIdk7YcJxl6MaGyQ/%5B!175055%5D-Extensions-Marketplace-Admin-Settings?node-id=1-108

vscode_extension_marketplace_settings_demo

How to set up and validate locally

1. Start GDK.
2. Through rails console (rails c) or the UI (/rails/features), be sure to enable web_ide_extensions_marketplace and vscode_extension_marketplace_settings.
3. Sign in to GDK with an admin account.
4. Visit Admin > Settings > General.
5. Visit VS Code Extension Marketplace section.
6. EXPECTATION: Toy with enabling/disabling and setting the Extension registry setting features.
7. EXPECTATION: Visit /-/profile/preferences to see how the extension marketplace settings affect the Enable extension marketplace opt-in for end users.