This is a follow-up patch to #6441.

Author: Andrew Or <andrew@databricks.com>

Closes #6510 from andrewor14/extends-funsuite-check and squashes the following commits:

6618b46 [Andrew Or] Exempt SparkSinkSuite from the FunSuite check
99d02ac [Andrew Or] Merge branch 'master' of github.com:apache/spark into extends-funsuite-check
48874dd [Andrew Or] Guard against direct uses of FunSuite / FunSuiteLike