turn on QSV_SKIP_FORMAT_CHECK env var for all property tests

[jqnatividad]

As property tests would sometimes produces random test input that causes the mime-type input checking introduced in #2304 to have false positive failures.

[jqnatividad]

instead of doing this, simplify input format checking to just scanning for supported file extensions (csv, tsv, tab, ssv), as the mime-type checking is prone to false positives.

Keep the QSV_SKIP_FORMAT env var to skip even this simplified scanning, as sometimes, some users use input with unconventional file extensions.