Upgrade MetaMask SDK to 2.1.0

[ecp4224]

PR-Codex overview

The focus of this PR is to refactor the MetaMask integration in the project by replacing MetaMaskUnity with MetaMaskSDK and updating socket handling.

Detailed summary

• Replaced MetaMaskUnity with MetaMaskSDK for MetaMask integration
• Updated socket handling in MetaMaskUnitySocketIO
• Refactored connection logic and session management

The following files were skipped due to too many changes: Assets/Thirdweb/Core/Plugins/MetaMask/Scripts/Providers/Sockets/MetaMaskUnitySocketIO.cs, Assets/Thirdweb/Core/Plugins/MetaMask/Resources/MetaMask/Prefabs/UI/OTP, Assets/Thirdweb/Core/Plugins/TextMesh

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