feat: add syncoor plugin for sync test monitoring

[reldothescribe]

This PR adds a Syncoor plugin for Ethereum sync test orchestration and monitoring.

Features

• List sync tests for a network
• Get sync progress and status
• Get client sync statistics (disk usage, memory, CPU, peers, sync percentage)
• Deep links to sync test pages

Implementation

Following the Dora plugin pattern:

• plugins/syncoor/ with config.go, plugin.go, examples.go, examples.yaml
• plugins/syncoor/python/syncoor.py - Python module
• Registered in builder.go
• Updated sandbox __init__.py

API Functions

• list_networks() - List networks with Syncoor instances
• list_tests(network, active_only=False) - List sync tests
• get_test(network, run_id) - Get detailed test information
• get_test_progress(network, run_id) - Get current progress metrics
• get_client_statistics(network, run_id) - Get client resource usage and sync stats
• link_test(network, run_id) - Deep link to test page
• link_tests_list(network) - Deep link to tests list page

Testing

• go build ./... passes
• go test ./... passes