chore: get signer address

[joepegler]

Requested by Venky, so that users can accommodate a custom signer in useAA

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PR-Codex overview

This PR adds a new function getSignerAddress to convertSigner.ts for retrieving signer addresses based on signer types.

Detailed summary

• Added getSignerAddress function to retrieve signer addresses
• Supports different signer types: Ethers, WalletClient, PrivateKeyAccount, AlchemySigner

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[github-actions]

size-limit report 📦

Path	Size
core (esm)	55.76 KB (+0.24% 🔺)
core (cjs)	60.96 KB (+0.18% 🔺)
account (tree-shaking)	53.21 KB (-0.2% 🔽)
bundler (tree-shaking)	2.54 KB (0%)
paymaster (tree-shaking)	2.23 KB (0%)
modules (tree-shaking)	41.08 KB (+0.13% 🔺)