feat: remove deprecated OKLink/XLayer, update documentation with named parameters

[VaitaR]

🎯 Changes Summary

This PR removes deprecated OKLink/XLayer scanner implementations and updates documentation to use named parameters for better clarity.

✅ What was done:

1. Removed OKLink/XLayer references - No longer supported scanner implementations
2. Removed deprecated BaseScanV1 - Base network now supported via Etherscan V2
3. Updated documentation - All examples now use named parameters for clarity
4. Updated docstrings - Reflect current scanner support
5. Removed OKLink parser - Cleaned up unused code
6. Updated test configurations - Reflect current scanner capabilities

🔧 Documentation Improvements:

Before (unclear):

client = ChainscanClient.from_config('blockscout', 'v1', 'blockscout_eth', 'eth')

After (clear):

client = ChainscanClient.from_config(
    scanner_name='blockscout',      # Provider name
    scanner_version='v1',           # API version
    scanner_id='blockscout_eth',    # Config identifier for Ethereum
    network='eth'                   # Network name
)

📋 Current Scanner Support:

Provider	scanner_name	scanner_version	scanner_id	network	API Key
BlockScout					❌ Not required
Etherscan					✅
Etherscan Base					✅
Moralis					✅

🎉 Benefits:

• 🧹 Cleaner codebase - Removed deprecated scanner implementations
• 📚 Better documentation - Named parameters make usage clear
• 🔧 Improved DX - Less confusion about parameter order
• 🚀 Future-ready - Base network properly integrated via Etherscan V2

✅ Testing:

• ✅ All existing tests pass
• ✅ Documentation examples work correctly
• ✅ Base network accessible via Etherscan V2
• ✅ No breaking changes for existing functionality