`optional_string_data_conversion`'s `Data` -> `String` rule should be optional

New Issue Checklist

• I've Updated SwiftLint to the latest version.
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Feature or Enhancement Proposal

In 0.57.0, the non_optional_string_data_conversion rule was split: the Data -> String conversion check was actually inverted and made its own rule. Unfortunately, as a default rule it's very heavy handed. In the vast majority of Swift apps, using String(decoding:as:) is perfectly correct, as non-UTF-8 strings are increasingly rare, and there often aren't any arbitrary strings at all. Additionally, using this initializer is an explicit acknowledgment that we don't care if the string isn't fully UTF-8. That is, we don't care if the decoding placeholder is inserted. That's may be a bug, but a far more minor one than not handling a string at all.

This part of the rule made optional by default.

Start by locating the optional_string_data_conversion rule and its default configuration; the issue explains that the Data-to-String check should not be enabled by default. Review the rule's existing tests, if present, and verify that the default configuration no longer reports this conversion while an opt-in configuration still does.