Move init_tools script into gitlab rails

Issue: Move init-tools.sh script into Rails repo (#520884 - closed)

What does this MR do and why?

This MR aims to move the functionality of init_tools.sh script that is a part of https://gitlab.com/gitlab-org/workspaces/gitlab-workspaces-tools/-/blob/main/scripts/init_tools.sh?ref_type=heads

This script is injected into the workspace and executed as part of the workspace initialization and we are moving the script content into the rails repo so that it can be executed directly as a startup command on workspace creation.

It also renames some workspace_variables from *_EDITOR_EXTENSIONS_GALLERY_* to *_VSCODE_EXTENSION_MARKETPLACE_*

References

Parent Epic: Startup scripts for Remote Development workspac... (&15602)

Screenshots or screen recordings

This MR does not contain any UI changes

Script Logs

How to set up and validate locally

• Setup workspaces locally following this guide
• Run bundle exec scripts/remote_development/run-smoke-test-suite.sh, all (non-flaky) tests should still pass
• Then go to http://gdk.test:3000/-/remote_development/workspaces and create a new workspace
• Check that the workspace is created successfully, open it -> make sure workspace features are functional
• Check that the log file was created and there are no errors during script execution. Run this in the workspace terminal cat ../workspace-logs/start_vscode.log
• Check that older workspaces are not affected by this change (restarts etc)

MR acceptance checklist

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

• init-tools.sh should be moved to the gitlab repo and deprecated in the gitlab-workspaces-tools repo
• Take this opportunity to rename all *_EDITOR_EXTENSIONS_GALLERY_* variables to *_VSCODE_EXTENSION_MARKETPLACE_*, to follow the new standard naming convention