DRILL-7936: Remove usage of Guava Files#createTempDir method
Guava's Files#createTempDir() method has some security issues, and since
better alternatives exist (including Java 7
Files#createTempDirectory(String) method), the function has been
deprecated in Guava 30.0 (but the security issues haven't been
addressed).
Introduce a drop-in replacement for this method in DrillFileUtils based
on the Java7 Files API and replace usage of the Guava method with the
new method in the codebase.
