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.
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