Add configurable processor class support #289

Job	Run time
cs-stan / Coding Standard & Static Analysis	16s
testsuite / testsuite-linux (8.1, pgsql, highest, false)	31s
testsuite / testsuite-linux (8.1, sqlite, lowest, false)	34s
testsuite / testsuite-linux (8.1, mysql, highest, false)	41s
testsuite / testsuite-linux (8.2, mysql, false)	34s
testsuite / testsuite-linux (8.3, sqlite, highest, false)	33s
testsuite / testsuite-linux (8.4, mysql, highest, false)	37s
	3m 46s

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