feat: Add explorer urls to gcs

[aletru01]

Description

This PR adds support for multiple blockchain explorers to clear signing functionality. Previously, the app only supported Etherscan links for Ethereum mainnet transactions. Now it supports explorer URLs for multiple networks including Arbitrum, Base, Optimism, and others.
The changes include:
A new explorer mapping system that maps chain IDs to their respective explorer URLs
URL generation based on the transaction's chain ID
Updated UI text to be more generic ("Scan to view on explorer" instead of "Scan to view on Etherscan")

These improvements enhance the user experience by ensuring the QR code redirects to a valid, network-specific explorer URL, allowing users to seamlessly verify their transactions on the correct chain.

Changes include

• Bugfix (non-breaking change that solves an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)
• Tests
• Documentation
• Other (for changes that might not fit in any category)

Additional comments

This PR was developed as part of the ETHGlobal hackathon.

Writing tests for this feature is challenging because Ragger’s navigator doesn’t currently support UI navigation through arrow clicks.

See: https://github.com/LedgerHQ/ragger/blob/master/src/ragger/navigator/navigation_scenario.py
https://github.com/LedgerHQ/app-ethereum/blob/develop/tests/ragger/test_gcs.py

[cedelavergne-ledger]

Thanks for your suggestion and contribution.
We'll look at this, but differently, because we are working on a feature allowing to give dynamic configuration at runtime, instead of updating the app for each network modification