Add deprecation warning for Util::mapClassNameToFileName #1333

# to view logs

Job	Run time
Windows - PHP 8.1 & SQL Server	2m 53s
Coding Standard & Static Analysis	22s
testsuite (8.1, sqlite)	37s
testsuite (8.1, mysql)	50s
testsuite (8.1, pgsql)	37s
testsuite (8.4, sqlite)	27s
testsuite (8.4, mysql)	49s
testsuite (8.4, pgsql)	48s
testsuite (8.2, mysql)	52s
testsuite (8.1, sqlite, prefer-lowest)	21s
	8m 36s

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