Add Plasma network and Sepolia testnet support with comprehensive documentation

Created by: ndrkltsk

Summary

• Add Plasma network configuration and integration for wallet-evm and wallet-evm-erc-4337 modules
• Add Sepolia testnet configuration with USDt ERC-20 mock/test token support
• Update quickstart guides with testnet options for developers to test without real funds
• Include faucet links (Pimlico and Candide) for obtaining test USDt on Sepolia
• Add legal notices clarifying testnet tokens are for testing only

Changes

Network Support

• Plasma: Added configuration with Candide bundler/paymaster support (chain ID: 9745)
• Sepolia: Added testnet configurations for both Pimlico and Candide paymasters (chain ID: 11155111)

Documentation Updates

• Updated wallet-evm and wallet-evm-erc-4337 configuration guides with Plasma and Sepolia examples
• Added testnet usage notes to wallet module usage documentation
• Updated network compatibility lists across README files
• Added provider configurations for Avalanche C-Chain, Plasma, and Sepolia

Developer Experience

• Added prominent testnet information in quickstart guides (Node.js and React Native)
• Included direct links to Pimlico and Candide faucets for obtaining test USDt
• Added disclaimers about testnet tokens
• Provided USDt Sepolia contract address and Etherscan links