[Nexus 2.0.0] Add Default Validator and clean 7702 init flows (AA-521)

[filmakarov]

• Add default validator mode

• Clean 7702 init flows s per AA-521 https://github.com/eth-infinitism/account-abstraction/pull/529/files#diff-e5a17bf464109f401b78513c9f091ed9874b8b0845c19ec7ea470fe5e665aa04
  we do not need custom flow for 770-2 accs at first validateUserOp, we can just use userOp.initcode for initdata

• Test it via ep v 0.8

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PR-Codex overview

This PR focuses on enhancing the Nexus smart contract with a default validator feature, improving module management, and updating related tests and interfaces.

Detailed summary

• Added MODE_DEFAULT_VALIDATOR constant.
• Updated Nexus constructor to accept a default validator and initialization data.
• Introduced DefaultValidatorCanNotBeInstalled error.
• Modified deployment tests to include default validator.
• Enhanced NexusBootstrap to initialize with a default validator.
• Updated ModuleManager to handle the default validator.
• Removed references to NexusSentinelListLib.
• Updated function signatures and logic to incorporate the default validator functionality.
• Improved test cases to cover new default validator scenarios.

✨ Ask PR-Codex anything about this PR by commenting with /codex {your question}

[openzeppelin-code]

Add Default Validator and clean 7702 init flows (AA-521)

Generated at commit: b1f784c90e34a2175aa843ee09f9264575431a34

🚨 Report Summary

	Severity Level	Results
Contracts	Critical High Medium Low Note Total	1 1 0 7 30 39

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For more details view the full report in OpenZeppelin Code Inspector

[github-actions]

🤖 Slither Analysis Report 🔎

Slither report

Details

# Slither report

THIS CHECKLIST IS NOT COMPLETE. Use --show-ignored-findings to show all the results.
Summary
🟡 - unused-return (3 results) (Medium)

• constable-states (2 results) (Optimization)

unused-return

🟡 Impact: Medium
🟡 Confidence: Medium

• ID-0
  ModuleManager._uninstallExecutor(address,bytes) ignores return value by executor.excessivelySafeCall(gasleft()(),0,0,abi.encodeWithSelector(IModule.onUninstall.selector,disableModuleData))

base/ModuleManager.sol#L287-L291

• ID-1
  ExecLib.hashExecutionBatch(Execution[]) ignores return value by a.set(i,executions[i].hashExecution())

lib/ExecLib.sol#L125-L139

• ID-2
  ModuleManager._uninstallValidator(address,bytes) ignores return value by validator.excessivelySafeCall(gasleft()(),0,0,abi.encodeWithSelector(IModule.onUninstall.selector,disableModuleData))

base/ModuleManager.sol#L247-L258

constable-states

Impact: Optimization
🔴 Confidence: High

• ID-3
  RegistryAdapter.registry should be constant

base/RegistryAdapter.sol#L10

• ID-4
  RegistryFactory.threshold should be constant

factory/RegistryFactory.sol#L38

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