[FIX] Restore utf8ByteLength to replace use of Buffer.byteLength()

[sbarrio]

What does this PR do?

Reported by #1122

This PR restores the utf8BtyeLength function introduced to replace Buffer.byteLength in order to support older environments where Buffer might not be available. This was mistakenly removed during a rebase when working on feature/v3. This was part of #1046

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