Add pmd rule to lint against using ST with global STGroup
Add pmd rule to lint against using ST with global STGroup

Summary: STGroup is not threadsafe. new ST() uses a default global STGroup which causes race conditions when using ST. lint against this usage

Reviewed By: cjhopman

fbshipit-source-id: 7ff4eb9ad7cedf3f7371b9f8b113cdef5a65a386

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