chore: test indexed auth keys

[horsefacts]

Change Summary

Add fork tests for indexed auth keys.

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PR-Codex overview

This PR focuses on modifying the registration of authentication keys in the AuthKeysTest contract, specifically changing how auth keys are created and registered with different indices.

Detailed summary

• Updated the creation of the auth key to include an index in authKey.
• Registered an auth key with index 0 using bytes.concat.
• Added functionality to register a new auth key with index 1.
• Created a new signature and metadata for the auth key with index 1.
• Added the new auth key to the keyGateway and verified its state.

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[github-actions]

Coverage after merging horsefacts/indexed-auth-keys into main will be

100.00%

Coverage Report

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
src
Bundler.sol	100%	100%	100%	100%
FnameResolver.sol	100%	100%	100%	100%
IdGateway.sol	100%	100%	100%	100%
IdRegistry.sol	100%	100%	100%	100%
KeyGateway.sol	100%	100%	100%	100%
KeyRegistry.sol	100%	100%	100%	100%
RecoveryProxy.sol	100%	100%	100%	100%
StorageRegistry.sol	100%	100%	100%	100%
src/abstract
EIP712.sol	100%	100%	100%	100%
Guardians.sol	100%	100%	100%	100%
Migration.sol	96.97%	80%	100%	100%	40
Nonces.sol	100%	100%	100%	100%
Signatures.sol	100%	100%	100%	100%
src/validators
SignedKeyRequestValidator.sol	100%	100%	100%	100%