[WIP] Implement Levenshtein distance for utf8_lcase collation

[viktorluc-db]

What changes were proposed in this pull request?

Supporting Levenshtein distance with utf8_lcase collation.

Why are the changes needed?

Levenshtein distance for utf8_lcase collation was not supported.

Does this PR introduce any user-facing change?

No.

How was this patch tested?

Unit tests in CollationSQLExpressionsSuite.

Was this patch authored or co-authored using generative AI tooling?

No.