Deprecate identifier collection approach. #670

Job	Run time
testsuite / testsuite-linux (8.1, lowest, false)	35s
testsuite / testsuite-linux (8.3, highest, false)	42s
testsuite / testsuite-linux (8.1, highest, false)	31s
testsuite / testsuite-linux (8.4, highest, false)	1m 21s
testsuite / testsuite-linux (8.2, highest, false)	35s
cs-stan / Coding Standard & Static Analysis	23s
	4m 7s

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