Optimization "select count(*) from table" stmtement , push down "count" type to BE.
support file type : parquet ，orc in hive .
1. 4kfiles , 60kwline num
before: 1 min 37.70 sec
after: 50.18 sec
2. 50files , 60kwline num
before: 1.12 sec
after: 0.82 sec
in previous [PR 12872](https://github.com/apache/doris/pull/12872), we convert multi equals on same slot into `in predicate`. for example, `a =1 or a = 2` => `a in (1, 2)`
This pr makes 4 changes about convert or to in:
1. fix a bug: `Not IN` is merged with equal. `a =1 or a not in (2, 3)` => `a in (1, 2, 3)`
2. extends this rule on more cases
- merge for more than one slot: 'a =1 or a = 2 or b = 3 or b = 4' => `a in (1, 2) or b in (3, 4)`
- merge skip not-equal and not-in: 'a =1 or a = 2 or b !=3 or c not in (1, 2)' => 'a in (1, 2) or b!=3 or c not in (1,2)`
3. rewrite recursively.
4. OrToIn is implemented in ExtractCommonFactorsRule. This rule will generate new exprs. OrToIn should apply on such generated exprs. for example `(a=1 and b=2) or (a=3 and b=4)` => `(a=1 or a=3) and (b=2 or b=4) and [(a=1 and b=2) or (a=3 and b=4)]` => `a in (1,3) and b in (2 ,4) and [(a=1 and b=2) or (a=3 and b=4)]`
In addition, this pr add toString() for some Expr.
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.
1.
In the "explain" result of SQL, the table name in `ScanNode` should be full qualified with dbname.
And for olap scan node, the selected index name should not be "null".
2.
Remove `tpch_sf1_p1/tpch_sf1/nereids/` in regression test, it will be fixed later.
