Fix upload new file in web ide test

What does this MR do and why?

This MR fixes and unquarantines the Web IDE file upload test by resolving multiple automation issues that were causing test failures.

1. Resolves File Picker Interference Issue

• Fixed issue where native OS file picker was blocking subsequent UI interactions
• Added JavaScript override to prevent automatic file input clicks that trigger the opening of OS native file picker
• Ensures clicking on create mr button programatically works without file pickering interference

2. Improves Window/Tab Management

• Enhanced logic for detecting and switching to new MR creation tabs
• Added proper waiting for new browser windows to open
• Fixed race conditions in tab switching

3. Unquarantines Previously Failing Test

• Removes test from quarantine
• Addresses issues from https://gitlab.com/gitlab-org/quality/test-failure-issues/-/issues/1603

Screenshots/Video

Screen Recording 2025-10-21 at 10.12.48 PM.mov

How to set up and validate locally

From the gitlab workspace

1. cd qa
2. bundle install

WEBDRIVER_HEADLESS=false GITLAB_QA_ADMIN_ACCESS_TOKEN=x QA_LOG_LEVEL=DEBUG QA_GITLAB_URL=https://gdk.test:3443 bundle exec rspec qa/specs/features/browser_ui/3_create/web_ide/upload_new_file_in_web_ide_spec.rb

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.

relates to https://gitlab.com/gitlab-org/quality/test-failure-issues/-/issues/1603