[Bug]: Memory exhaustion when recreating duplicates-index

[natted]

Expected behavior

command bin/console cmf:duplicates-index -r will recreate the customer duplicates index successfully

Actual behavior

When executing bin/console cmf:duplicates-index -r with a large amount of Customers that have many potential duplicates, recreateIndex within /src/DuplicatesIndex/DefaultMariaDbDuplicatesIndex.php fails due to memory exhaustion (before reindexing is completed).

Steps to reproduce

Import large number of Customers, with large amount of potential duplicates.
Run command bin/console cmf:duplicates-index -r

[kingjia90]

Fixed by #512