Add Sepolia support for Polygon cross-chain#751

Draft

michalinacienciala wants to merge 3 commits intomainfrom

sepolia-support-polygon

Commits on Nov 22, 2023

Add Sepolia support for Polygon cross-chain
michalinacienciala
committed

Commits on Nov 29, 2023

Update Polygon cross-chain config to support Amoy testnet
michalinacienciala
committed

Commits on Jan 26, 2024

Add Sepolia-related `external` contracts
michalinacienciala
committed