in previous pr(#14876) we compact equals like "a=1 or a=2 or a = 3 " in to "a in (1, 2, 3)"
this pr set a lower bound for the number of equals COMPACT_EQUAL_TO_IN_PREDICATE_THRESHOLD (default is 2)
for performance reason, we create a hashSet to collect literals, like {1,2,3}. and hence, the literals in "in-predicates" are in random order.
for regression test, if we need stable output of explain string, set COMPACT_EQUAL_TO_IN_PREDICATE_THRESHOLD to a large number to avoid compact rule.
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