Fix invalid UTF-8 encoding in YAML files

All file reads now replacewith "PERLQQ" quoting from the Encode module
and do not warn.
remove legacy PERL_CORE
v1.4411

    [FIXED]

    - Invalid UTF-8 encoding in YAML files are now replaced with "PERLQQ"
      quoting from the Encode module and without warnings.

    - Removed legacy test modifications for $ENV{PERL_CORE}
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