[rqlrewrite] Fix rewrite on ambiguities introduced by NOT relation or "is IN" type restriction When some inserted RQL snippet generate more solutions than the original RQL, the rewriter attempt to duplicate the snippet for each newly introduced solution. There are though some cases where we do not want this behaviour in case of ambiguities introduced by: * NOT(X relation Y) expression, since it won't be equivalent to NOT(X relation Y1, Y1 is Type1) OR NOT(X relation Y2, Y2 is Type2) ; * EXISTS(X relation Y, Y is IN (Type1, Type2) expression, since it's not actually necessary to split an explicitly introduced ambiguity (and it crash if we attempt to do so, so...). In test, we've to modify the `rewrite()` function because in the newly introduced test we need the same constraint to be applied to two variables in the original query, and this was not supported before. Notice the generated RQL in test is still *NOT CORRECT* "(EXISTS(NOT EXISTS() OR EXISTS(...))", or at least isn't optimal. This will be fixed in a forthcoming changeset. Related to #17074119

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