Fix wiki pages and artists to normalize other names more consistently
and correctly.
For wiki pages, we strip leading / trailing / repeated underscores to
fix user typos, and we normalize to NFKC form to make search more consistent.
For artists, we allow leading / trailing / repeated underscores because
some artist names have these, and we normalize to NFC form because some
artists have weird names that would be lost by NFKC form. This does make
search less consistent.
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