feat: add base sepolia and opt sepolia

[alex-miao]

PR-Codex overview

This PR focuses on adding support for the Sepolia network in various modules.

Detailed summary

• Added support for baseSepolia network in utils.ts, chains.ts, and defaults.ts files.
• Added support for optimismSepolia network in utils.ts, chains.ts, and defaults.ts files.
• Added support for arbitrumSepolia network in chains.ts and defaults.ts files.

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[avasisht23]

can you take a look here and see where else to add these new chains in the other packages?

For instance, I see we added baseGoerli here in the alchemy package.