PR Summary

• Replace StringCollection with List<string>.
• Replace StringCollection with string[] when length is known.
• Rename variables for clarity.
• Refactor GenerateMultiLineRowField as static method.
• Cache loop invariant integers.

Changes not made in the following:
src\System.Management.Automation\engine\LanguagePrimitives.cs: complex call hierarchy
src\Microsoft.PowerShell.Commands.Diagnostics\CounterSet.cs: parameter in public API

PR Context

Performance using the generic List<string> is much better than using the non-generic StringCollection.

See #13425 (comment) for a benchmark.

PR Checklist

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