Use default admin role in TimelockController

[JulissaDantes]

Fixes #3389

The TimelockController contract currently uses a custom non-zero TIMELOCK_ADMIN role, in order to make easier the introduction of new roles without custom migrations the DEFAULT_ADMIN_ROLE needs to be used.

PR Checklist

• Tests
• Documentation
• Changelog entry

[socket-security]

Socket Security Pull Request Report

👍 No dependency changes detected in pull request

Pull request report summary

Issue	Status
Install scripts	✅ 0 issues
Native code	✅ 0 issues
Bin script confusion	✅ 0 issues
Bin script shell injection	✅ 0 issues
Unresolved require	✅ 0 issues
Invalid package.json	✅ 0 issues
HTTP dependency	✅ 0 issues
Git dependency	✅ 0 issues
Potential typo squat	✅ 0 issues
Known Malware	✅ 0 issues
Telemetry	✅ 0 issues
Protestware/Troll package	✅ 0 issues

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[Amxx]

That PR looks way bigger than it needs to be.

[frangio]

Seems like the PR includes everything from master. Those are things we want to merge into next-v5.0 because we need to keep it up to date but we should do it separately.

[JulissaDantes]

Now it's ready!

[frangio]

@JulissaDantes Can you rebase on next-v5.0? Goal would be to remove these commits from the commit list:

[Amxx]

do we want that ?