[E2E] [QIT] Add Jetpack connection support for QIT E2E tests

[mgascam]

Fixes #WOOPMNT-5336

Changes proposed in this Pull Request

This is a stacked PR that builds on top of the basic QIT E2E testing functionality to address the key challenge of establishing a Jetpack connection for WooPayments in test environments.

The previous foundation established basic E2E testing infrastructure, but lacked the ability to connect WooPayments to a real test account via Jetpack. This PR solves that by providing automated Jetpack connection setup for already onboarded test accounts.

Key features:

1. WP-CLI QIT Development Commands: New WP_CLI_QIT_Dev_Command class providing:

   • wp woopayments qit_setup - Configures Jetpack connection for pre-onboarded test sites
   • wp woopayments qit_status - Shows connection status for debugging
   • Automatic test mode configuration and account data refresh from server

2. Enhanced E2E Test Runner: Updated e2e-runner.sh with:

   • Plugin build caching based on source file signatures (avoids unnecessary rebuilds)
   • Jetpack credential passing via environment variables

3. Connection Validation Tests:

   • Tests to verify WooPayments shows configuration options (not Connect screen)
   • Validation that account data is properly fetched from the server

4. Configuration Management:

   • Added E2E Jetpack credential support in default.env template
   • Environment variable handling for site ID, blog token, and user token

Why This Approach:
The added WP-CLI commands are doing pretty much the same as the WCPay Dev Tools that we use for the current E2E tests. Initially I tried to use this dev plugin, but it turned out to be tricky to download and install it in the QIT environment. I came with this workaround inspired by the work @dmvrtx did in his draft #10811. But initializating a test drive account turned out to be tricky, so I went with the approach of using an already onboarded account. So, essentially, I'm following the same approach that we have in the current E2E tests, but adapted to the QIT needs. I'd love to hear any ideas for improving this part, but I guess the current approach could work for the time being. It's worth noting that the WP-CLI commands are only registered in development/local environments for security.

Testing instructions

Prerequisites:

• QIT CLI installed and configured (ie. run composer install)
• Access to a pre-onboarded WooPayments test account with Jetpack credentials. The following steps worked well for me:
  1. Spin a fresh JN site with WooCommerce, WooPayments and Jetpack Debug Tools
  2. Follow the minimum steps to onboard with a test account
  3. Go to Jetpack Debug > Broken Token to find the current tokens and blog ID
  4. Copy tests/qit/config/default.env to tests/qit/config/local.env
  5. Fill in E2E credentials from your onboarded test account:

E2E_JP_SITE_ID=your_site_id_here
E2E_JP_BLOG_TOKEN=your_blog_token_here
E2E_JP_USER_TOKEN=your_user_token_here

Running the tests:

1. Run E2E tests: npm run test:qit-e2e
2. Connection validation tests should pass

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