Replace ArrayList with List<T>

[iSazonov]

PR Summary

Related #10315

Replace ArrayList where we use it unjustifiably to get more readable and reliable code.

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[iSazonov]

@daxian-dbw @anmenaga Could you please review?

[iSazonov]

@adityapatwardhan Could you please review the small style PR?

[ghost]

🎉v7.0.0-preview.4 has been released which incorporates this pull request.:tada:

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