gh-69456: Add method to detect if a string contains surrogates

[StanFromIreland]

Request @bitdancer (and maybe @ezio-melotti and @malemburg (looking at devguide))

contains_surrogates is misleading since it does not require more than one, and to me, singular suffers less, though it can be misleading too.

And, should this also be implemented for bytes?

• Issue: Add method to detect if a string contains surrogates #69456

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