hpc:Make sure files are being read/written in UTF-8

Addition of readFileUtf8 and writeFileUtf8 and make hpc use them. It would be better to move those functions into hpc library, this way readTix could use it as well. But in all honesty, I think it would be best to have them available in base, but that is a long shot. In any case, I adjusted the imports a bit, so if functions with the same names will get added to Trace.Hpc.Utils, they will not mess anything up here.

Fixes #17073 (closed).

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